Remove direct push detection GitHub action

We are trying out not allowing direct pushes anymore, so this is not necessary anymore, unless we later revert it again (unlikely): https://github.com/NixOS/nixpkgs/issues/249117

.github/workflows/direct-push.yml

@@ -1,37 +0,0 @@
-name: "Direct Push Warning"
-on:
-  push:
-    branches:
-     - master
-     - release-**
-permissions:
-  contents: read
-
-jobs:
-  build:
-    permissions:
-      contents: write  # for peter-evans/commit-comment to comment on commit
-    runs-on: ubuntu-latest
-    if: github.repository_owner == 'NixOS'
-    env:
-      GITHUB_SHA: ${{ github.sha }}
-      GITHUB_REPOSITORY: ${{ github.repository }}
-    steps:
-    - name: Check if commit is a merge commit
-      id: ismerge
-      run: |
-        ISMERGE=$(curl -H 'Accept: application/vnd.github.groot-preview+json' -H "authorization: Bearer ${{ secrets.GITHUB_TOKEN }}" https://api.github.com/repos/${{ env.GITHUB_REPOSITORY }}/commits/${{ env.GITHUB_SHA }}/pulls | jq -r '.[] | select(.merge_commit_sha == "${{ env.GITHUB_SHA }}") | any')
-        echo "ismerge=$ISMERGE" >> $GITHUB_OUTPUT
-    # github events are eventually consistent, so wait until changes propagate to thier DB
-    - run: sleep 60
-      if: steps.ismerge.outputs.ismerge != 'true'
-    - name: Warn if the commit was a direct push
-      if: steps.ismerge.outputs.ismerge != 'true'
-      uses: peter-evans/commit-comment@v2
-      with:
-        body: |
-          @${{ github.actor }}, you pushed a commit directly to master/release branch
-          instead of going through a Pull Request.
-
-          That's highly discouraged beyond the few exceptions listed
-          on https://github.com/NixOS/nixpkgs/issues/118661