clang format bump 21

Author: mrousavy

.github/workflows/validate-cpp.yml

@@ -28,7 +28,7 @@ jobs:
       - name: Run clang-format style check
         uses: mrousavy/clang-format-action@v1
         with:
-          clang-format-version: '16'
+          clang-format-version: '21'
           check-path: ${{ matrix.path }}
           clang-format-style-path: package/.clang-format