PYTHON-5401: Refactor PR template for clarity and conciseness (#363)

Author: Jibola

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,38 +1,29 @@
-[Issue Key](https://jira.mongodb.org/browse/{ISSUE_KEY})
+<!-- Thanks for contributing! -->
+<!-- Please ensure that the title of the PR is in the following form:
+[JIRA TICKET]: Issue Title
 
-## Summary
-
-<!-- What is this PR introducing? If context is already provided from the JIRA ticket, still place it in the Pull Request as you should not make the reviewer do digging for a basic summary. -->
+If you are an external contributor and there is no JIRA ticket associated with your change, then use your best judgement
+for the PR title. A MongoDB employee will create a JIRA ticket and edit the name and links as appropriate.
+-->
+[JIRA TICKET](https://jira.mongodb.org/browse/%7BJIRA_TICKET%7D)
 
 ## Changes in this PR
-
-<!-- What changes did you make to the code? What new APIs (public or private) were added, removed, or edited to generate the desired outcome explained in the above summary? -->
+<!-- What changes did you make to the code? What new APIs (public or private) were added, removed, or edited to generate
+the desired outcome explained in the above summary? -->
 
 ## Test Plan
-
-<!-- How did you test the code? If you added unit tests, you can say that. If you didn’t introduce unit tests, explain why. All code should be tested in some way – so please list what your validation strategy was. -->
-
-### Screenshots (optional)
-
-<!-- Usually a great supplement to a test plan, especially if this requires local testing. -->
+<!-- How did you test the code? If you added unit tests, you can say that. If you didn’t introduce unit tests, explain why.
+All code should be tested in some way – so please list what your validation strategy was. -->
 
 ## Checklist
-
-<!-- Do not delete the items provided on this checklist -->
+<!-- Do not delete the items provided on this checklist. -->
 
 ### Checklist for Author
-
 - [ ] Did you update the changelog (if necessary)?
-- [ ] Is the intention of the code captured in relevant tests?
-- [ ] If there are new TODOs, has a related JIRA ticket been created?
-
-### Checklist for Reviewer {@primary_reviewer}
+- [ ] Is there test coverage?
+- [ ] Is any followup work tracked in a JIRA ticket? If so, add link(s).
 
+### Checklist for Reviewer
 - [ ] Does the title of the PR reference a JIRA Ticket?
 - [ ] Do you fully understand the implementation? (Would you be comfortable explaining how this code works to someone else?)
-- [ ] Have you checked for spelling & grammar errors?
 - [ ] Is all relevant documentation (README or docstring) updated?
-
-## Focus Areas for Reviewer (optional)
-
-<!-- List any complex portion of code you believe needs particular scrutiny and explain why.  -->