Update pr template checkboxes to bullets (#3158)

Author: lrapoport-cf

.github/pull_request_template.md

@@ -11,9 +11,9 @@ Fixes # [insert GH or internal issue number(s)].
 - [ ] Tests
 - [ ] Changeset ([Changeset guidelines](https://github.com/cloudflare/workers-sdk/blob/main/CONTRIBUTING.md#changesets))
 
-**Reviewer has performed the following, where applicable:**
+**Reviewer is to perform the following, as applicable:**
 
-- [ ] Checked for inclusion of relevant tests
-- [ ] Checked for inclusion of a relevant changeset
-- [ ] Checked for creation of associated docs updates
-- [ ] Manually pulled down the changes and spot-tested
+- Checked for inclusion of relevant tests
+- Checked for inclusion of a relevant changeset
+- Checked for creation of associated docs updates
+- Manually pulled down the changes and spot-tested