Revert "Make 403 non-fatal for manifest existence checks (google#1691)"

This reverts commit a927d7c.

pkg/v1/remote/pusher.go

@@ -386,9 +386,6 @@ func (rw *repoWriter) writeChild(ctx context.Context, child partial.Describable,
 	return nil
 }
 
-// TODO: Consider caching some representation of the tags/digests in the destination
-// repository as a hint to avoid this optimistic check in cases where we will most
-// likely have to do a PUT anyway, e.g. if we are overwriting a tag we just wrote.
 func (rw *repoWriter) manifestExists(ctx context.Context, ref name.Reference, t Taggable) (bool, error) {
 	f := &fetcher{
 		target: ref.Context(),
@@ -412,14 +409,6 @@ func (rw *repoWriter) manifestExists(ctx context.Context, ref name.Reference, t
 			if terr.StatusCode == http.StatusNotFound {
 				return false, nil
 			}
-
-			// We treat a 403 here as non-fatal because this existence check is an optimization and
-			// some registries will return a 403 instead of a 404 in certain situations.
-			// E.g. https://jfrog.atlassian.net/browse/RTFACT-13797
-			if terr.StatusCode == http.StatusForbidden {
-				logs.Debug.Printf("manifestExists unexpected 403: %v", err)
-				return false, nil
-			}
 		}
 
 		return false, err