Update the documentation comment for parseFile().
Update the documentation comment for parseFile().

Bug: https://github.com/dart-lang/sdk/issues/49512
Change-Id: I74a558be91055b3fae24b4e5db3f70875dc7a218
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/252706
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