Change to CMake 3.21.2 to fix test failures (#363, #394)

This should fix problem with accumulation of labels with ctest_test().

.github/workflows/tribits_testing.yml

@@ -23,7 +23,7 @@ jobs:
           - { os: ubuntu-latest, cmake: "3.18.6", generator: "makefiles", python: "3.8", cc: gcc-9,  cxx: g++-9,  fc: gfortran-9  }
           - { os: ubuntu-latest, cmake: "3.19.8", generator: "makefiles", python: "3.8", cc: gcc-9,  cxx: g++-9,  fc: gfortran-9  }
           - { os: ubuntu-latest, cmake: "3.20.5", generator: "makefiles", python: "3.8", cc: gcc-9,  cxx: g++-9,  fc: gfortran-9  }
-          - { os: ubuntu-latest, cmake: "3.21.0", generator: "makefiles", python: "3.8", cc: gcc-9,  cxx: g++-9,  fc: gfortran-9  }
+          - { os: ubuntu-latest, cmake: "3.21.2", generator: "makefiles", python: "3.8", cc: gcc-9,  cxx: g++-9,  fc: gfortran-9  }
 
     runs-on: ${{ matrix.config.os }}