[Signin][Android] Link tests OWNERS to the main OWNERS

This CL links signin javatest and junit OWNERS to the main OWNERS file.

Bug: None
Change-Id: I70b10eb8d62f2b2b9573cb28c9f037a0177d1f69
Reviewed-on: https://chromium-review.googlesource.com/803514
Commit-Queue: Boris Sazonov <bsazonov@chromium.org>
Reviewed-by: Ted Choc <tedchoc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#521326}

chrome/android/javatests/src/org/chromium/chrome/browser/signin/OWNERS

-bsazonov@chromium.org
-gogerald@chromium.org
+file://chrome/android/java/src/org/chromium/chrome/browser/signin/OWNERS
 
 # COMPONENT: Services>Signin

chrome/android/junit/src/org/chromium/chrome/browser/signin/OWNERS

+file://chrome/android/java/src/org/chromium/chrome/browser/signin/OWNERS
+
+# COMPONENT: Services>Signin