mautrix-telegram: stop flagging matrix_mautrix_telegram_scheme as a removed variable

The bridgev2 (Go) rewrite removed matrix_mautrix_telegram_scheme (the old
Python bridge's public web-login endpoint scheme) and added a deprecation
check for it. We later reintroduced a variable of the same name to configure
the bridge's HTTP API exposure address, but the deprecation entry remained.

Because the check matches any defined variable (via ansible.builtin.varnames),
not just user-set ones, it tripped for every install with the Telegram bridge
enabled, even when the user never set it.

Drop the deprecation entry, since the variable is a current one again. The
related (still removed) matrix_mautrix_telegram_hostname and
matrix_mautrix_telegram_path_prefix entries are kept.

Closes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/5368
Regression since d2252db4fe

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

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

@@ -30,7 +30,7 @@
     - {'old': 'matrix_mautrix_telegram_container_repo_version', 'new': 'matrix_mautrix_telegram_container_image_self_build_branch'}
     # Variables removed in the bridgev2 (Go) rewrite — mautrix-telegram no longer has a Python runtime,
     # a separate lottieconverter container or a web-based login endpoint.
-    - {'old': 'matrix_mautrix_telegram_scheme', 'new': '<removed (the bridge no longer has a public web-based login endpoint)>'}
+    # (matrix_mautrix_telegram_scheme was part of this group too, but has since been reintroduced to configure the bridge's HTTP API exposure address, so it's intentionally not listed here.)
     - {'old': 'matrix_mautrix_telegram_hostname', 'new': '<removed (the bridge no longer has a public web-based login endpoint)>'}
     - {'old': 'matrix_mautrix_telegram_path_prefix', 'new': '<removed (the bridge no longer has a public web-based login endpoint)>'}
     - {'old': 'matrix_mautrix_telegram_public_endpoint', 'new': '<removed (the bridge no longer has a public web-based login endpoint)>'}