Fix git-latest ansible-lint errors

Reference: https://ansible-lint.readthedocs.io/en/latest/default_rules/#git-latest

Our variable naming is not necessarily consistent across roles.
I've tried to follow the naming conventions of each individual role.
All new variables are suffixed with `_version`, but the prefix may be
somewhat different.

roles/matrix-bridge-mautrix-googlechat/defaults/main.yml

@@ -6,6 +6,7 @@ matrix_mautrix_googlechat_enabled: true
 
 matrix_mautrix_googlechat_container_image_self_build: false
 matrix_mautrix_googlechat_container_image_self_build_repo: "https://github.com/mautrix/googlechat.git"
+matrix_mautrix_googlechat_container_image_self_build_repo_version: "{{ 'master' if matrix_mautrix_googlechat_version == 'latest' else matrix_mautrix_googlechat_version }}"
 
 matrix_mautrix_googlechat_version: v0.3.3
 # See: https://mau.dev/mautrix/googlechat/container_registry

roles/matrix-bridge-mautrix-googlechat/tasks/setup_install.yml

@@ -63,6 +63,7 @@
 - name: Ensure Mautrix Hangots repository is present on self build
   ansible.builtin.git:
     repo: "{{ matrix_mautrix_googlechat_container_image_self_build_repo }}"
+    version: "{{ matrix_mautrix_googlechat_container_image_self_build_repo_version }}"
     dest: "{{ matrix_mautrix_googlechat_docker_src_files_path }}"
     force: "yes"
   become: true