update admin email to uri

changelog.d/3687.feature

@@ -1 +1 @@
-set admin email via config, to be used in error messages where the user should contact the administrator
+set admin uri via config, to be used in error messages where the user should contact the administrator

synapse/config/server.py

@@ -82,7 +82,7 @@ class ServerConfig(Config):
         self.hs_disabled = config.get("hs_disabled", False)
         self.hs_disabled_message = config.get("hs_disabled_message", "")
 
-        # Admin email to direct users at should their instance become blocked
+        # Admin uri to direct users at should their instance become blocked
         # due to resource constraints
         self.admin_uri = config.get("admin_uri", None)