XFA - Default background in rectangle is white

- Fix a typo in order to open the pdf in issue #13679
  - After fixing the fill default color there wer some regressions because of z-index
    and when fixing z-index there were some regressions because of borders
  - So fix the borders rendering.

web/xfa_layer_builder.css

@@ -31,7 +31,6 @@
   text-align: initial;
   top: 0;
   left: 0;
-  z-index: 200;
   transform-origin: 0 0;
   line-height: 1.2;
 }
@@ -76,26 +75,6 @@
   vertical-align: 0;
 }
 
-.xfaDraw {
-  z-index: 100;
-}
-
-.xfaExclgroup {
-  z-index: 200;
-}
-
-.xfaField {
-  z-index: 300;
-}
-
-.xfaRich {
-  z-index: 300;
-}
-
-.xfaSubform {
-  z-index: 200;
-}
-
 .xfaCaption {
   overflow: hidden;
   flex: 0 1 auto;