Enhance find_unreleased_changelog_items action to check for merged PRs

[nfelt14]

Proposed changes

This PR enhances the find_unreleased_changelog_items to check for merged PRs before succeeding.

Types of changes

What types of changes does your code introduce?
Put an x in the boxes that apply

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Functionality update (non-breaking change which updates or changes existing functionality)
• CI/CD update (an update to the CI/CD workflows, scripts, and/or configurations)

Checklist

Put an x in the boxes that apply. You can also fill these out after creating the PR. If you're unsure about any of them, don't hesitate to ask. We're here to help! This is simply a reminder of what we are going to look for before merging your code.

• I have followed the guidelines in the CONTRIBUTING document
• I have signed the CLA
• I have checked to ensure there aren't other open Pull Requests for the same update/change
• I have created (or updated) an Issue to track the status of this update/change and updated the link in this PR description (see above in the Proposed changes section) using the wording Addresses #<issue_number>
• I have performed a self-review of my code
• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• Basic linting passes locally with my changes
• I have added necessary documentation (if appropriate)
• I have updated the Changelog with a brief description of my changes

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (55821c1) to head (e2063a4).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main       #74   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            4         4           
  Lines          208       211    +3     
  Branches        39        40    +1     
=========================================
+ Hits           208       211    +3     

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[github-actions]

Test Results (ubuntu)

path	passed	subtotal
tests/test_bump_version_in_files.py	5	5
tests/test_create_unique_testpypi_version.py	7	7
tests/test_find_unreleased_changelog_items.py	6	6
tests/test_update_development_dependencies.py	13	13
TOTAL	31	31

Link to workflow run

[github-actions]

Test Results (windows)

path	passed	subtotal
tests\test_bump_version_in_files.py	5	5
tests\test_create_unique_testpypi_version.py	7	7
tests\test_find_unreleased_changelog_items.py	6	6
tests\test_update_development_dependencies.py	13	13
TOTAL	31	31

Link to workflow run

[github-actions]

Test Results (macos)

path	passed	subtotal
tests/test_bump_version_in_files.py	5	5
tests/test_create_unique_testpypi_version.py	7	7
tests/test_find_unreleased_changelog_items.py	6	6
tests/test_update_development_dependencies.py	13	13
TOTAL	31	31

Link to workflow run