cmake: install specific version to suppress installation error

Author: patapenka-alexey

.github/workflows/testing.yml

@@ -59,6 +59,10 @@ jobs:
       - name: Setup tt environment
         run: tt init
 
+      # Waiting until `checks` repo will be updated.
+      - name: Install specific CMake version
+        run: pip3 install cmake==3.15.3
+
       - name: Setup Tarantool ${{ matrix.tarantool }}
         if: matrix.tarantool != 'master'
         uses: tarantool/setup-tarantool@v2