[iOS][Credential-Provider] Add OWNERS

Bug: 1066803
Change-Id: I559b6f45f84b9ca587257acdcb51236838caf17f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2131914
Commit-Queue: Javier Ernesto Flores Robles <javierrobles@chromium.org>
Reviewed-by: Mark Cogan <marq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#755322}

ios/chrome/browser/credential_provider/OWNERS

+javierrobles@chromium.org
+djean@chromium.org
+
+# TEAM: ios-directory-owners@chromium.org
+# OS: iOS