Ensure git cloning when self-building is done with the matrix user, not root

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/1749

roles/matrix-email2matrix/tasks/setup_install.yml

@@ -39,6 +39,8 @@
     dest: "{{ matrix_email2matrix_docker_src_files_path }}"
     version: "{{ matrix_email2matrix_container_image_self_build_branch }}"
     force: "yes"
+  become: true
+  become_user: "{{ matrix_user_username }}"
   register: matrix_email2matrix_git_pull_results
   when: "matrix_email2matrix_container_image_self_build|bool"