/join and /room/:roomId/join aren't exact aliases

Separate them, clarify their differences.

Also, fix some links which weren't being properly populated.

templating/matrix_templates/units.py

@@ -440,17 +440,6 @@ class MatrixUnits(Units):
 
                 endpoints.append(endpoint)
 
-                aliases = single_api.get("x-alias", None)
-                if aliases:
-                    alias_link = aliases["canonical-link"]
-                    for alias in aliases["aliases"]:
-                        endpoints.append({
-                            "method": method.upper(),
-                            "path": alias,
-                            "alias_for_path": full_path,
-                            "alias_link": alias_link
-                        })
-
         return {
             "base": api.get("basePath").rstrip("/"),
             "group": group_name,