[api-minor] Remove the disableCombineTextItems option

*Please note:* This parameter has never been used within the PDF.js library/viewer itself, and it was only ever added for backwards compatibility reasons.

This parameter was added in PR 7475, over six years ago, to try and optionally maintain the previous *default* text-extraction behaviour.
However as part of the general text-extraction improvements in PR 13257, almost two years ago, the `disableCombineTextItems` functionality was accidentally "broken" in various ways. Note how the only (very basic) unit-test was updated in a way that doesn't really make sense, since generally speaking you'd expect that using the option should result in *more* (or at least the same number of) text-items. Furthermore there's also the recent issue 16209, where the option causes almost all textContent to be concatenated together.

Hence this patch proposes that we simply remove the `disableCombineTextItems` option since it's essentially unused/untested functionality, as evident from the fact that it took almost two years for someone to notice that it's broken.

src/core/annotation.js

@@ -1010,7 +1010,6 @@ class Annotation {
       task,
       resources,
       includeMarkedContent: true,
-      combineTextItems: true,
       sink,
       viewBox,
     });

src/core/document.js

@@ -511,13 +511,7 @@ class Page {
     });
   }
 
-  extractTextContent({
-    handler,
-    task,
-    includeMarkedContent,
-    sink,
-    combineTextItems,
-  }) {
+  extractTextContent({ handler, task, includeMarkedContent, sink }) {
     const contentStreamPromise = this.getContentStream();
     const resourcesPromise = this.loadResources([
       "ExtGState",
@@ -545,7 +539,6 @@ class Page {
         task,
         resources: this.resources,
         includeMarkedContent,
-        combineTextItems,
         sink,
         viewBox: this.view,
       });

src/core/evaluator.js

@@ -2236,7 +2236,6 @@ class PartialEvaluator {
     task,
     resources,
     stateManager = null,
-    combineTextItems = false,
     includeMarkedContent = false,
     sink,
     seenStyles = new Set(),
@@ -2534,11 +2533,7 @@ class PartialEvaluator {
         return false;
       }
 
-      if (
-        !combineTextItems ||
-        !textState.font ||
-        !textContentItem.prevTransform
-      ) {
+      if (!textState.font || !textContentItem.prevTransform) {
         return true;
       }
 
@@ -3191,7 +3186,6 @@ class PartialEvaluator {
                     task,
                     resources: xobj.dict.get("Resources") || resources,
                     stateManager: xObjStateManager,
-                    combineTextItems,
                     includeMarkedContent,
                     sink: sinkWrapper,
                     seenStyles,

src/core/worker.js

@@ -741,7 +741,7 @@ class WorkerMessageHandler {
     });
 
     handler.on("GetTextContent", function (data, sink) {
-      const pageIndex = data.pageIndex;
+      const { pageIndex, includeMarkedContent } = data;
 
       pdfManager.getPage(pageIndex).then(function (page) {
         const task = new WorkerTask("GetTextContent: page " + pageIndex);
@@ -755,8 +755,7 @@ class WorkerMessageHandler {
             handler,
             task,
             sink,
-            includeMarkedContent: data.includeMarkedContent,
-            combineTextItems: data.combineTextItems,
+            includeMarkedContent,
           })
           .then(
             function () {

src/display/api.js

@@ -1120,8 +1120,6 @@ class PDFDocumentProxy {
  * Page getTextContent parameters.
  *
  * @typedef {Object} getTextContentParameters
- * @property {boolean} disableCombineTextItems - Do not attempt to combine
- *   same line {@link TextItem}'s. The default value is `false`.
  * @property {boolean} [includeMarkedContent] - When true include marked
  *   content items in the items array of TextContent. The default is `false`.
  */
@@ -1602,17 +1600,13 @@ class PDFPageProxy {
    * @param {getTextContentParameters} params - getTextContent parameters.
    * @returns {ReadableStream} Stream for reading text content chunks.
    */
-  streamTextContent({
-    disableCombineTextItems = false,
-    includeMarkedContent = false,
-  } = {}) {
+  streamTextContent({ includeMarkedContent = false } = {}) {
     const TEXT_CONTENT_CHUNK_SIZE = 100;
 
     return this._transport.messageHandler.sendWithStream(
       "GetTextContent",
       {
         pageIndex: this._pageIndex,
-        combineTextItems: disableCombineTextItems !== true,
         includeMarkedContent: includeMarkedContent === true,
       },
       {