Make it clear that you don't *always* need to build from scratch to test

The checklist is long and arduous, and a great idea for complex changes,
but not needed for folks who are simpling routing through a variable to
be overridden in the internal repos.

.github/PULL_REQUEST_TEMPLATE.md

@@ -8,4 +8,4 @@ Make sure that the following steps are done before merging:
     - [ ] Update the appropriate internal repo (be sure to update for all our environments)
     - [ ] If you are updating a secure value rather than an internal one, file a DEVOPS ticket with details.
     - [ ] Add an entry to the CHANGELOG.
-  - [ ] Have you performed the proper testing specified on the [Ops Ansible Testing Checklist](https://openedx.atlassian.net/wiki/display/EdxOps/Ops+Ansible+Testing+Checklist)?
+  - [ ] If you are making a complicated change, have you performed the proper testing specified on the [Ops Ansible Testing Checklist](https://openedx.atlassian.net/wiki/display/EdxOps/Ops+Ansible+Testing+Checklist)?  Adding a new variable does not require the full list (although testing on a sandbox is a great idea to ensure it links with your downstream code changes).