Fix Telegram bridge HTTP proxying when not using matrix-nginx-proxy

From what I see, this was never implemented to begin with.

Fixes #189 (Github Issue).

roles/matrix-bridge-mautrix-telegram/tasks/validate_config.yml

@@ -9,3 +9,12 @@
     - "matrix_mautrix_telegram_api_id"
     - "matrix_mautrix_telegram_api_hash"
     - "matrix_mautrix_telegram_public_endpoint"
+
+- name: (Deprecation) Catch and report renamed Telegram variables
+  fail:
+    msg: >-
+      Your configuration contains a variable, which now has a different name.
+      Please change your configuration to rename the variable (`{{ item.old }}` -> `{{ item.new }}`).
+  when: "item.old in vars"
+  with_items:
+    - {'old': 'matrix_mautrix_telegram_container_exposed_port_number', 'new': '<superseded by matrix_mautrix_telegram_container_http_host_bind_port>'}