gopls: update codereview.cfg for the v0.8 branch

For golang/go#51074

Change-Id: I54e73fa4ee7ce57e78482e53aed25a10047ae745
Reviewed-on: https://go-review.googlesource.com/c/tools/+/384134
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
gopls-CI: kokoro <noreply+kokoro@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
diff --git a/codereview.cfg b/codereview.cfg
index 3f8b14b..644796a 100644
--- a/codereview.cfg
+++ b/codereview.cfg
@@ -1 +1,4 @@
 issuerepo: golang/go
+branch: gopls-release-branch.0.8
+parent-branch: master
+