Fix formatting in PR template checklist

[rapsealk]

What does this PR do?

Follow-up of ab90975.

This pull request makes a small change to the .github/pull_request_template.md file, improving the formatting of the checklist section by consolidating multiline checklist items into single lines for better readability.

I found the checklist in current PR template is somewhat broken as below:

Checklist

• This PR fixes a minor issue (e.g.: typo or small bug) or improves the docs (you can dismiss the other
  checks if that's the case).
• This change is discussed in a Github issue/
  discussion (please add a
  link).
• The documentation and docstrings adhere to the
  documentation guidelines.
• This change includes necessary high-coverage tests.
  (No quality testing = no merge!)

[rapsealk]

Was it meant to improve readability?

[vfdev-5]

It was created 3 years ago. We can make each line as a single line. I have no strong opinion.

[cgarciae]

Thanks @rapsealk !