[infra] Remove stephana@ from OWNERS

He's being set as reviewer for recipe rolls, which causes the rest of us
not to see them.

Change-Id: Idaa59e32ba3fa28d2843a263e6fd8a0d0e234657
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/222776
Reviewed-by: Ravi Mistry <rmistry@google.com>
Commit-Queue: Eric Boren <borenet@google.com>
1 file changed