Delete extraneous check-macos-11-cmake-clang job.

At this point, we have a `cmake` build on both macOS 11 and 12.

It makes more sense to drop one of them (`11`), given that the
environment and toolchain are exercised by the `make` job on the
same platform.

That allows us to simplify our CI pipeline.

Author: NlightNFotis

.github/workflows/pull-request-checks.yaml

@@ -432,48 +432,6 @@ jobs:
       - name: Run JBMC regression tests
         run: make -C jbmc/regression test-parallel JOBS=3
 
-  check-macos-11-cmake-clang:
-    runs-on: macos-11
-    steps:
-      - uses: actions/checkout@v2
-        with:
-          submodules: recursive
-      - name: Fetch dependencies
-        run: brew install cmake ninja maven flex bison ccache z3
-      - name: Confirm z3 solver is available and log the version installed
-        run: z3 --version
-      - name: Download cvc5 binary and make sure it can be deployed
-        run: |
-          curl -L https://github.com/cvc5/cvc5/releases/download/cvc5-${{env.cvc5-version}}/cvc5-macOS --output cvc5
-          chmod u+x cvc5
-          mv cvc5 /usr/local/bin
-          cvc5 --version
-      - name: Prepare ccache
-        uses: actions/cache@v2
-        with:
-          path: .ccache
-          key: ${{ runner.os }}-Release-${{ github.ref }}-${{ github.sha }}-PR
-          restore-keys: |
-            ${{ runner.os }}-Release-${{ github.ref }}
-            ${{ runner.os }}-Release
-      - name: ccache environment
-        run: |
-          echo "CCACHE_BASEDIR=$PWD" >> $GITHUB_ENV
-          echo "CCACHE_DIR=$PWD/.ccache" >> $GITHUB_ENV
-      - name: Zero ccache stats and limit in size
-        run: ccache -z --max-size=500M
-      - name: Configure using CMake
-        run: |
-          mkdir build
-          cd build
-          cmake .. -G Ninja -DCMAKE_BUILD_TYPE=Release -DCMAKE_C_COMPILER=/usr/bin/clang -DCMAKE_CXX_COMPILER=/usr/bin/clang++ -Dsat_impl=glucose
-      - name: Build with Ninja
-        run: cd build; ninja -j3
-      - name: Print ccache stats
-        run: ccache -s
-      - name: Run CTest
-        run: cd build; ctest -V -L CORE . -j3
-
   check-macos-12-cmake-clang:
     runs-on: macos-12
     steps: