Update error message in MyTischtennisUrlController for clarity

Modified the error handling in MyTischtennisUrlController to specify that only the URL is required, enhancing the clarity of the error response. This change aligns with recent efforts to standardize error handling across the application.

backend/controllers/myTischtennisUrlController.js

@@ -21,7 +21,7 @@ class MyTischtennisUrlController {
       const { url } = req.body;
 
       if (!url) {
-        throw new HttpError('URL and clubTeamId are required', 400);
+        throw new HttpError('URL is required', 400);
       }
 
       // Validate URL