…` action

8865686 fix: adjust conditions in `Check Merge Fast-Forward Only` action (UdjinM6)

Pull request description:

  ## Issue being fixed or feature implemented
  I _think_ we were using the wrong event name since #6190... which is why #6341 is failing atm.

  ```
  V Run git fetch origin master:master
    git fetch origin master:master
    git checkout master
    if [ "pull_request_target" == "pull_request" ]; then
      git merge --ff-only 0172b88
    else
      git merge --ff-only d494339
    fi

  ```
  https://github.com/dashpay/dash/actions/runs/11474383519/job/31930192140?pr=6341

  ## What was done?

  ## How Has This Been Tested?

  Pushed these changes to my `develop` https://github.com/UdjinM6/dash/commits/develop/

  Created 2 PRs to verify it worked as expected:
  - UdjinM6#18
  - UdjinM6#19

  ## Breaking Changes
  n/a

  ## Checklist:
  - [ ] I have performed a self-review of my own code
  - [ ] I have commented my code, particularly in hard-to-understand areas
  - [ ] I have added or updated relevant unit/integration/functional/e2e tests
  - [ ] I have made corresponding changes to the documentation
  - [ ] I have assigned this pull request to a milestone _(for repository code-owners and collaborators only)_

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Tree-SHA512: fb38b671d072b802eda0cd012df805cfb875e537b3049ee4b254af0b2763ad12e916972509899948d71910ca439c036d63b678e26761ad111e63b65d5e824a2b