Fix issue when test pinging a monitor endpoint (#410)

* do not include body when method is HEAD

* simplify checks for including request body

apps/web/src/app/api/checker/regions/_checker.ts

···
       ...headers,
     },
     // Avoid having "TypeError: Request with a GET or HEAD method cannot have a body." error
-    ...(data.method !== "GET" && { body: data?.body }),
+    ...(data.method === "POST" && { body: data?.body }),
   });
 
   return res;