Fix async backend ResultSingle messag

Author: robsdedude

testkitbackend/_async/requests.py

@@ -366,7 +366,9 @@ async def ResultNext(backend, data):
 
 async def ResultSingle(backend, data):
     result = backend.results[data["resultId"]]
-    await backend.send_response("Record", totestkit.record(result.single()))
+    await backend.send_response("Record", totestkit.record(
+        await result.single()
+    ))
 
 
 async def ResultPeek(backend, data):

testkitbackend/_sync/requests.py

@@ -366,7 +366,9 @@ def ResultNext(backend, data):
 
 def ResultSingle(backend, data):
     result = backend.results[data["resultId"]]
-    backend.send_response("Record", totestkit.record(result.single()))
+    backend.send_response("Record", totestkit.record(
+        result.single()
+    ))
 
 
 def ResultPeek(backend, data):