Patches should be submitted to master, not maint

Update SUBMITTING_PATCHES accordingly.

Change-Id: I6fd57a84c67d3762f1f23276d95cac2aeecd5e8f

SUBMITTING_PATCHES

@@ -5,7 +5,7 @@ Short Version:
  - Make sure all code is under the Apache License, 2.0.
  - Publish your changes for review:
 
-   git push https://gerrit-review.googlesource.com/git-repo HEAD:refs/for/maint
+   git push https://gerrit-review.googlesource.com/git-repo HEAD:refs/for/master
 
 
 Long Version:
@@ -71,7 +71,7 @@ Push your patches over HTTPS to the review server, possibly through
 a remembered remote to make this easier in the future:
 
    git config remote.review.url https://gerrit-review.googlesource.com/git-repo
-   git config remote.review.push HEAD:refs/for/maint
+   git config remote.review.push HEAD:refs/for/master
 
    git push review