Upgrade to dartdoc-0.30.2.
Upgrade to dartdoc-0.30.2.

Change-Id: I7e53334582e96590fc738e04fa33a1f4a9a3b4b3
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/138600
Auto-Submit: Janice Collins <f6a8c838e29d3fa8813240c8bed106e760081e0e@google.com>
Reviewed-by: Paul Berry <72d414e3a99fb120308437779d51667bcc0984eb@google.com>
Reviewed-by: Samuel Rawlins <5cf2cac5eec2ad6d0eb2b0f4ff6af9a590ce2bf6@google.com>
Commit-Queue: Janice Collins <f6a8c838e29d3fa8813240c8bed106e760081e0e@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk