Remove unnecessary 'implements Element' for implementing UriReferencedElement.
Remove unnecessary 'implements Element' for implementing UriReferencedElement.

Change-Id: I789d1ca4b4853cbb496eeebd899e493e0031ffd3
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/246045
Reviewed-by: Brian Wilkerson <1f7641b6b14c52b9163524ab8d9aabff80176f21@google.com>
Commit-Queue: Konstantin Shcheglov <09e4d7516628963212bf4aace2f97603d2b706e4@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