Update analyzer pubspec to reflect dependency on collection.
Update analyzer pubspec to reflect dependency on collection.

The dependency was added in 27a32754955886d65f0b73a803de8c45af44c961.
Note that analyzer previously had a transitive dependency on
collection.

R=scheglov@google.com

Review URL: https://codereview.chromium.org/2536373004 .

dart-archive/dart-sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-lang/sdk,dartino/dart-sdk,dart-lang/sdk