Revert "Temporarily add the Dart model team as owners of pkg/analyzer/api.txt"

This reverts commit 97ba123.

Reason for revert: The new analyzer element model is stable now; the only work that remains is to remove the old deprecated model (once all clients in google3 have been moved off it).

Original change's description:
> Temporarily add the Dart model team as owners of pkg/analyzer/api.txt
>
> This should help speed up the review process during the process of
> migrating to the new element model API.
>
> Change-Id: I7d2f974df351c6b82dc0d315f2f4bf547704674e
> Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/414825
> Commit-Queue: Paul Berry <[email protected]>
> Reviewed-by: Konstantin Shcheglov <[email protected]>
> Auto-Submit: Paul Berry <[email protected]>

Change-Id: I261249b322ed82db2a9fa6388b30bbbd05272350
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/421420
Commit-Queue: Paul Berry <[email protected]>
Reviewed-by: Konstantin Shcheglov <[email protected]>

Author: stereotype441

pkg/analyzer/OWNERS

@@ -5,7 +5,6 @@ file:/tools/OWNERS_MODEL
 # reviewed by the developer experience team.
 per-file api.txt=set noparent
 per-file api.txt=file:/tools/OWNERS_DEVELOPER_EXPERIENCE
-per-file api.txt=file:/tools/OWNERS_MODEL
 per-file api.txt=file:/OWNERS # (For last resort global approvers)
 
 # messages.yaml contains error message text, so it should be