use the HTTP facade instead of manually creating a new request

This allows consuming applications to use Http::fake() to mock the FileMaker Data API.

src/Services/FileMakerConnection.php

@@ -697,7 +697,7 @@ protected function prepareRequestForSending($request = null)
             if (method_exists(Factory::class, 'createPendingRequest')) {
                 $request = Http::createPendingRequest();
             } else {
-                $request = new PendingRequest();
+                $request = Http::acceptJson();
             }
         }