clarify "Homeserver name" in synadm config

Closes: #142

this config is used consistently throughout synadm as the homeserver
name/the domain part of the MXID

synadm/cli/__init__.py

@@ -207,7 +207,8 @@ def get_redacted_token_prompt(cli_token):
             default=timeout if timeout else helper.config.get(
                 "timeout", timeout)),
         "homeserver": click.prompt(
-            "Homeserver name (auto-retrieval or matrix.DOMAIN)",
+            "Homeserver name (\"auto-retrieval\" or the domain part in your "
+            "MXID)",
             default=homeserver if homeserver else helper.config.get(
                 "homeserver", homeserver)),
         "ssl_verify": click.prompt(