[ci] Drop GitHub Action seanmiddleditch/gha-setup-ninja (#6044)

From the GitHub Action README: "This action is no longer
necessary, as ninja is now included on all default
GitHub runner instances."

Author: gruenich

.github/workflows/ci.yml

@@ -1191,9 +1191,6 @@ jobs:
       - name: Update CMake
         uses: jwlawson/actions-setup-cmake@v2.2
 
-      - name: Install ninja-build tool
-        uses: seanmiddleditch/gha-setup-ninja@v6
-
       - name: Run pip installs
         run: |
           python -m pip install --upgrade pip