Use the ESLint no-restricted-syntax rule to ensure that assert is always called with two arguments

Having `assert` calls without a message string isn't very helpful when debugging, and it turns out that it's easy enough to make use of ESLint to enforce better `assert` call-sites.
In a couple of cases the `assert` calls were changed to "regular" throwing of errors instead, since that seemed more appropriate.

Please find additional details about the ESLint rule at https://eslint.org/docs/rules/no-restricted-syntax

src/core/obj.js

@@ -578,7 +578,11 @@ class Catalog {
             }
             break;
           default:
-            assert(typeof value === "boolean");
+            if (typeof value !== "boolean") {
+              throw new FormatError(
+                `viewerPreferences - expected a boolean value for: ${key}`
+              );
+            }
             prefValue = value;
         }