Fix the remaining var-spacing ansible-lint errors

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

roles/matrix-bridge-appservice-slack/defaults/main.yml

@@ -115,7 +115,7 @@ matrix_appservice_slack_registration_yaml: |
     - exclusive: false
       regex: '#{{ matrix_appservice_slack_user_prefix }}.*'
     rooms: []
-  url: "{{matrix_appservice_slack_appservice_url}}:{{ matrix_appservice_slack_matrix_port }}"
+  url: "{{ matrix_appservice_slack_appservice_url }}:{{ matrix_appservice_slack_matrix_port }}"
   sender_localpart: slackbot
   rate_limited: true
   protocols: null