ci: removed mirror.yml since we no longer use GitLab

Related PR https://github.com/manticoresoftware/manticoresearch/pull/4233

.github/workflows/mirror.yml

@@ -1,42 +0,0 @@
-name: 🪞 Mirror
-run-name: 🪞 Mirror ${{ github.sha }}
-
-on:
-  push:
-    branches:
-      - master
-      - maintenance-release
-      - 'manticore-*'
-
-# waits until the previous workflow run to finish when a new one appears
-concurrency:
-  group: mirror_${{ github.ref }}
-
-jobs:
-
-  to_gitlab:
-    name: Sync to GitLab
-    if: github.repository == 'manticoresoftware/manticoresearch'
-    runs-on: ubuntu-latest
-    steps:
-      - name: Commit info
-        run: |
-          echo "# Syncing commit ${{ github.sha }} to GitLab" >> $GITHUB_STEP_SUMMARY
-          echo "* Commit URL: [${{ github.sha }}](/${{ github.repository }}/commit/${{ github.sha }})" >> $GITHUB_STEP_SUMMARY
-          echo "* Initiated by: [@${{ github.actor }}](https://github.com/${{ github.actor }})" >> $GITHUB_STEP_SUMMARY
-          echo "* Ref: ${{ github.ref_type }} \"${{ github.ref_name }}\"" >> $GITHUB_STEP_SUMMARY
-          echo "* Attempt: ${{ github.run_attempt }}" >> $GITHUB_STEP_SUMMARY
-      - name: Checkout repository
-        uses: actions/checkout@v3
-        with:
-          token: ${{ secrets.GITHUB_TOKEN }}
-          fetch-depth: 0
-      - name: Sync to Gitlab
-        run: |
-          echo "${{ secrets.GITLAB_SSH_KEY }}" > /tmp/ssh.key
-          chmod 600 /tmp/ssh.key
-          git remote add gitlab [email protected]:manticoresearch/dev.git
-          git checkout ${{ github.ref }}
-          GIT_SSH_COMMAND='ssh -i /tmp/ssh.key -o IdentitiesOnly=yes -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -F /dev/null' git fetch gitlab
-          GIT_SSH_COMMAND='ssh -i /tmp/ssh.key -o IdentitiesOnly=yes -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -F /dev/null' git push -u gitlab ${{ github.ref }}
-        shell: bash