Try don't use the REST API to get PR message in CI build

[ArkadiuszMichalski]

Actually we use REST API (https://api.github.com) to get PR message:

notepad-plus-plus/.github/workflows/CI_build.yml

Line 38 in aa6a55c

$last_commit = @(Invoke-RestMethod ${{ github.event.pull_request._links.commits.href }})[0] | Select-Object -Last 1

I noticed that this API is limited , and I experienced this limit myself recently. It would be best to avoid using this approach if possible, or as a last resort add authentication to increase the limit.

I'll try to find some command directly in git that will return the message of the last commit in PR (Github Action does not expose this information directly or I haven't figured it out yet).