[github] pull request template: fix checklist markdown formatting

Closes #3522

(Internal change: 2356158)

.github/pull_request_template.md

@@ -6,14 +6,14 @@
 
 ### Checklist
 
-[ ] I have created this PR based on the dev branch
+- [ ] I have created this PR based on the dev branch
 
-[ ] I have followed the [coding conventions](https://openusd.org/release/api/_page__coding__guidelines.html)
+- [ ] I have followed the [coding conventions](https://openusd.org/release/api/_page__coding__guidelines.html)
 
-[ ] I have added unit tests that exercise this functionality (Reference: 
-[testing guidelines](https://openusd.org/release/api/_page__testing__guidelines.html))
+- [ ] I have added unit tests that exercise this functionality (Reference: 
+  [testing guidelines](https://openusd.org/release/api/_page__testing__guidelines.html))
 
-[ ] I have verified that all unit tests pass with the proposed changes
+- [ ] I have verified that all unit tests pass with the proposed changes
 
-[ ] I have submitted a signed Contributor License Agreement (Reference: 
-[Contributor License Agreement instructions](https://openusd.org/release/contributing_to_usd.html#contributor-license-agreement))
+- [ ] I have submitted a signed Contributor License Agreement (Reference: 
+  [Contributor License Agreement instructions](https://openusd.org/release/contributing_to_usd.html#contributor-license-agreement))