[release-branch.go1.17] update codereview.cfg for release-branch.go1.17

The initial "branch: master" configuration was inherited from when
the release-branch.go1.17 branch was branched off the master branch.
Update the "branch" key, otherwise a modern git-codereview will mail
CLs to the wrong branch.

We can set "parent-branch" so that 'git codereview sync-branch' works
to merge latest master into release-branch.go1.17, something we want
to do for subsequent RCs, maybe up to the final release. (At some point
the release freeze will end and tree will open for Go 1.18 development,
so we'll be switching to using cherry-picks only. Having parent-branch
will not be useful then, but I think harmless.)

Change-Id: I36ab977eaeb52bc0a84cc59e807572054f54c789
Reviewed-on: https://go-review.googlesource.com/c/go/+/334376
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Heschi Kreinick <heschi@google.com>
Trust: Dmitri Shuralyov <dmitshur@golang.org>
diff --git a/codereview.cfg b/codereview.cfg
index 77a74f1..9d5ebe8 100644
--- a/codereview.cfg
+++ b/codereview.cfg
@@ -1 +1,2 @@
-branch: master
+branch: release-branch.go1.17
+parent-branch: master