feat: Update pull_request_template checklist

[cbartz]

Applicable spec: n/a

Overview

Update the pull request template checklist with "The release notes are updated"

Also the list of appropriate PR labels is updated.

Rationale

This is required to comply with the standard documentation policy

Checklist

• The charm style guide was applied
• The contributing guide was applied
• The changes are compliant with ISD054 - Managing Charm Complexity
• The documentation is generated using src-docs
• The documentation for charmhub is updated
• The PR is tagged with appropriate label (urgent, trivial, complex)

[github-actions]

Test coverage for c29546f

Name           Stmts   Miss Branch BrPart  Cover   Missing
----------------------------------------------------------
src/charm.py      31      0      4      0   100%
----------------------------------------------------------
TOTAL             31      0      4      0   100%

Static code analysis report

Run started:2025-01-10 13:44:01.624415

Test results:
  No issues identified.

Code scanned:
  Total lines of code: 151
  Total lines skipped (#nosec): 0
  Total potential issues skipped due to specifically being disabled (e.g., #nosec BXXX): 0

Run metrics:
  Total issues (by severity):
  	Undefined: 0
  	Low: 0
  	Medium: 0
  	High: 0
  Total issues (by confidence):
  	Undefined: 0
  	Low: 0
  	Medium: 0
  	High: 0
Files skipped (0):