build(aio): don't render `@Annotation` tags (#24000)

Because we were "ignoring" these tags they were being
rendered as part of the previous tag.
What we really want to do is know about them, so that we
don't break the doc-gen but then ignore them when rendering.

PR Close #24000

aio/tools/transforms/angular-api-package/tag-defs/Annotation.js

@@ -1,4 +1,5 @@
-// A ts2dart compiler annotation that can be ignored in API docs.
+// A ts2dart compiler annotation that we don't care about for API docs.
+// But, if we don't have a tag-def for it the doc-gen will error.
 module.exports = function() {
-  return {name: 'Annotation', ignore: true};
+  return {name: 'Annotation'};
 };