Update PULL_REQUEST_TEMPLATE.md

Since now the PR has to be sent to the predev rather than develop, the incoming PR's need to be consistent with the predev.

Author: anubhakushwaha

docs/PULL_REQUEST_TEMPLATE.md

@@ -3,7 +3,7 @@
 
 **Checklist**
 
-- [ ] My branch is up-to-date with the upstream `develop` branch.
+- [ ] My branch is up-to-date with the upstream `predev` branch.
 - [ ] I have added necessary documentation (if appropriate).
 
 **Which issue does this PR fix?**: fixes #