build(docs-infra): add sealed markers to classes in API pages (#42807)

This change will mark classes as `sealed` unless they have been annotated
with an `@extensible` jsdoc tag.

Fixes #42802

PR Close #42807

aio/src/styles/2-modules/api-pages/_api-pages.scss

@@ -97,7 +97,6 @@
 
         .github-links {
           a {
-
             .material-icons:hover {
               background: none;
             }
@@ -167,6 +166,10 @@
     margin-top: 8px;
   }
 
+  .final-message {
+    font-style: italic;
+  }
+
   .api-heading {
     @include mixins.font-size(14);
     margin: 16px;

aio/src/styles/2-modules/label/_label-theme.scss

@@ -8,9 +8,17 @@
     &.api-status-label {
       background-color: constants.$mediumgray;
 
-      &.deprecated, &.security, &.impure-pipe {
+      &.deprecated,
+      &.security,
+      &.impure-pipe {
         background-color: constants.$brightred;
       }
+
+      a {
+        color: inherit;
+        line-height: inherit;
+        font-size: inherit;
+      }
     }
 
     &.api-type-label {