ci: GitHub Actions cache key includes conan.lock for conan dependencies

Author: henryborchers

.github/workflows/tox_matrix.yml

@@ -68,7 +68,7 @@ jobs:
         uses: actions/cache@v3
         with:
           path: "${{steps.conan-path-script.outputs.result}}/.conan2"
-          key: ${{ runner.os }}-conan-${{ hashFiles('conanfile.py') }}
+          key: ${{ runner.os }}-conan-${{ hashFiles('conanfile.py') }}-${{ hashFiles('conan.lock') }}
 
       - name: Prebuild Conan packages (Windows)
         if: |