Update recording_with_microphone.rst

Author: toivocat

tutorials/audio/recording_with_microphone.rst

@@ -42,7 +42,7 @@ An ``AudioStreamPlayer`` named ``AudioStreamRecord`` is used for recording.
         var idx = AudioServer.get_bus_index("Record")
         # And use it to retrieve its first effect, which has been defined
         # as an "AudioEffectRecord" resource.
-        effect = AudioServer.get_bus_effect(idx, 0)
+        var effect = AudioServer.get_bus_effect(idx, 0)
 
  .. code-tab:: csharp