Warning StatusIcon should use black fill for a11y

To ensure proper contrast for a11y purposes, the warning status icon
should use a black fill for the '!' in the middle. The default is
transparent which means that in the light theme the contrast is not
sufficient to meet minimum accessibility requirements.

packages/components/src/components/StatusIcon/StatusIcon.scss

@@ -1,5 +1,5 @@
 /*
-Copyright 2020-2022 The Tekton Authors
+Copyright 2020-2023 The Tekton Authors
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at
@@ -43,6 +43,10 @@ limitations under the License.
 
     &.tkn--status-icon--type-inverse {
       fill: $support-03;
+
+      path:first-child {
+        fill: black;
+      }
     }
   }
 }