fix: use correct matrix property

Author: jackhodgkiss

.github/workflows/pull_request.yml

@@ -35,7 +35,7 @@ jobs:
         run: |
           pipx uninstall ansible-core
           python3 -m pip install --upgrade pip
-          python3 -m pip install ansible-core==${{ matrix.ansible }}.* docker git+https://github.com/stackhpc/ansible-modules-hashivault@c22434d887f0b8a5ac3ebda710664a027291e71c  # yamllint disable-line rule:line-length
+          python3 -m pip install ansible-core==${{ matrix.ansible_version }}.* docker git+https://github.com/stackhpc/ansible-modules-hashivault@c22434d887f0b8a5ac3ebda710664a027291e71c  # yamllint disable-line rule:line-length
           ansible-galaxy collection build
           ansible-galaxy collection install *.tar.gz