style: Remove unnecessary spaces around concatenation operators in ValidateSignatureFlexible middleware.

app/Http/Middleware/ValidateSignatureFlexible.php

@@ -16,7 +16,7 @@ public function handle(Request $request, Closure $next)
         }
 
         // Pakai APP_URL, bukan request scheme
-        $baseUrl = rtrim(config('app.url'), '/') . '/' . ltrim($request->path(), '/');
+        $baseUrl = rtrim(config('app.url'), '/').'/'.ltrim($request->path(), '/');
 
         $query = collect($request->query())
             ->except('signature')