Update PR template to reflect new merging strategy

.github/pull_request_template.md

@@ -21,7 +21,7 @@
 
 Self checklist (all need to be checked):
 - [ ] The developer has manually tested the changes and verified that the changes work
-- [ ] The commits have meaningful messages (squashes happen on merge by the bot).
+- [ ] The developer has squashed their branch so it contains _only one commit_, with a meaningful message (don't do this if merging a feature branch into main or incubation).
 - [ ] Testing instructions have been added in the PR body (for PRs involving changes that are not immediately obvious).
 - [ ] The developer has added tests or explained why testing cannot be added (unit tests & storybook for related changes)