The linter is moved from third_party to pkg, and the old copy has
been removed from DEPS for weeks now. Remove the workaround that
ignores an old copy of linter in third_party/pkg/linter.
Users who have updated without running gclient sync -D will
now get an error that they have two copies of the
linter package, and they will get a message that they should
run gclient sync -D when they run gclient sync.
This completes the migration of the linter package into the SDK
source repository.
This reverts most of https://dart-review.googlesource.com/c/sdk/+/321722
leaving a small refactoring cleanup in place.
Bug: https://github.com/dart-lang/linter/issues/4411
Change-Id: Id5cdb3485e42e78743303d64370bc9f7899ad00e
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/325301
Reviewed-by: Jonas Termansen <sortie@google.com>
Reviewed-by: Phil Quitslund <pquitslund@google.com>
Commit-Queue: William Hesse <whesse@google.com>
