ENH: Bump CMake to v3.21.3

Addresses Windows cxx build warnings due to MSVC discovery issues that
were fixed in CMake v3.21.3

https://gitlab.kitware.com/cmake/cmake/-/merge_requests/6497

Author: tbirdso

.github/workflows/build-test-cxx.yml

@@ -52,7 +52,7 @@ jobs:
         python -m pip install ninja
 
     - name: Get specific version of CMake, Ninja
-      uses: lukka/get-cmake@v3.18.3
+      uses: lukka/get-cmake@v3.21.3
 
     - name: Download ITK
       run: |