Remove color from "params" syntax class

HLJS emits a syntax class for function parameters which the PolyGerrit
syntax stylesheet would color blue. However, HLJS did not always apply
this class accurately, for example, in the C++ case described in the
linked issue.

Because the class was not very informative anyway, and the HLJS default
stylesheet does not style it either, this change removes it from the
PolyGerrit syntax styles.

Bug: Issue 4975
Change-Id: I26ed0b8f745ac6add994a5d1cfc8eb1303dac8cf

polygerrit-ui/app/elements/diff/gr-syntax-layer/gr-syntax-layer.js

@@ -64,7 +64,6 @@
     'gr-diff gr-syntax gr-syntax-string': true,
     'gr-diff gr-syntax gr-syntax-selector-id': true,
     'gr-diff gr-syntax gr-syntax-title': true,
-    'gr-diff gr-syntax gr-syntax-params': true,
     'gr-diff gr-syntax gr-syntax-comment': true,
     'gr-diff gr-syntax gr-syntax-meta': true,
     'gr-diff gr-syntax gr-syntax-meta-keyword': true,

polygerrit-ui/app/elements/diff/gr-syntax-themes/gr-theme-default.html

@@ -60,7 +60,6 @@ limitations under the License.
       .gr-syntax-meta-keyword {
         color: #219;
       }
-      .gr-syntax-params,
       .gr-syntax-type {
         color: #00f;
       }