chore: slightly update PR template

.github/PULL_REQUEST_TEMPLATE.md

@@ -7,24 +7,22 @@
 ## Checklist
 
 <!--
-- Answer the questions below, choosing the section(s) relevant to your PR.
+- Answer the questions below, choosing the section(s) relevant to your PR. Non-applying sections shall be set to "closed".
 - Place an `x` in the [ ] for yes, leave it empty for no. If a question is not applicable, remove the [ ], but keep the message in place.
 - Use the Preview tab to confirm the PR will render correctly.
 -->
 
-- [ ] I have read and acknowledged the [response policy](https://github.com/pypdfium2-team/pypdfium2#contributions).
-
 ### Helpers
+<details open>
 
 - [ ] This PR changes helpers code.
 - [ ] The change comes with sufficient test cases to confirm correct functionality.
 - [ ] Any new test files are under a suitable license and have been registered in `reuse/dep5`.
 
-### Other
-
-- [ ] This PR changes other things, namely: ... <!-- briefly specify what was changed -->
+</details>
 
 ### Setup
+<details open>
 
 - [ ] This PR changes setup code (`setupsrc/`, `setup.py` etc.).
 - [ ] I have read through relevant doc sections [Installation -> From source][1] and [Setup Magic][2].
@@ -37,3 +35,12 @@
 [1]: https://github.com/pypdfium2-team/pypdfium2?tab=readme-ov-file#install-source
 [2]: https://github.com/pypdfium2-team/pypdfium2?tab=readme-ov-file#setup-magic
 [3]: https://github.com/pypdfium2-team/pypdfium2?tab=readme-ov-file#install-source-caller
+
+</details>
+
+### Other
+<details open>
+
+- [ ] This PR changes other things, namely: ... <!-- sum up change (keyword/topic) -->
+
+</details>