content test: Remove test that's redundant with testContentSmoke test

In the 'inline math' group just above this, we have the following test:

  testContentSmoke(ContentExample.mathInline);

Looks like the behavior of that test differs from this one, just in
not passing `findRichText: true`. But that didn't stop it from
finding the expected text and passing, so, shrug.

Author: chrisbobbe

test/widgets/content_test.dart

@@ -1041,11 +1041,6 @@ void main() {
         targetFontSizeFinder: mkTargetFontSizeFinderFromPattern(r'\lambda'));
     });
 
-    testWidgets('displays KaTeX content', (tester) async {
-      await prepareContent(tester, plainContent(ContentExample.mathInline.html));
-      tester.widget(find.text('λ', findRichText: true));
-    });
-
     testWidgets('fallback to displaying KaTeX source if unsupported KaTeX HTML', (tester) async {
       await prepareContent(tester, plainContent(ContentExample.mathInlineUnknown.html));
       tester.widget(find.text(r'\lambda'));