fix: Eventloop unclosed (#796)

When I call ragas in the fastapi, every time I call it, python will have
an open event loop (/proc/self/fd).

Author: yunfwe

src/ragas/executor.py

@@ -96,7 +96,7 @@ def run(self):
             results = self.loop.run_until_complete(self._aresults())
         finally:
             self.results = results
-            self.loop.stop()
+            self.loop.close()
 
 
 @dataclass