Fix self-building for matrix-registration-bot

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/2919

roles/custom/matrix-bot-matrix-registration-bot/defaults/main.yml

@@ -5,7 +5,7 @@
 matrix_bot_matrix_registration_bot_enabled: true
 matrix_bot_matrix_registration_bot_container_image_self_build: false
 matrix_bot_matrix_registration_bot_docker_repo: "https://github.com/moan0s/matrix-registration-bot.git"
-matrix_bot_matrix_registration_bot_docker_repo_version: "{{ matrix_bot_matrix_registration_bot_version if matrix_bot_matrix_registration_bot_version != 'latest' else 'main' }}"
+matrix_bot_matrix_registration_bot_docker_repo_version: "{{ 'main' if matrix_bot_matrix_registration_bot_version == 'latest' else ('v' + matrix_bot_matrix_registration_bot_version) }}"
 matrix_bot_matrix_registration_bot_docker_src_files_path: "{{ matrix_bot_matrix_registration_bot_base_path }}/docker-src"
 
 matrix_bot_matrix_registration_bot_version: 1.3.0