feat(aio): render hover status on code-tabs (#24027)

The Material Design spec states that there should be a change
of background when hovering over a tab label.

See https://material.io/design/components/tabs.html#states

Related to #23985

PR Close #24027

aio/src/styles/2-modules/_code.scss

@@ -106,6 +106,9 @@ aio-code pre {
 }
 
 .code-tab-group .mat-tab-label {
+  &:hover {
+    background: rgba(black, 0.04);
+  }
   white-space: nowrap;
 }