chore(reaction): add missing count_details return type annotation (#3269)

Author: vmphase

discord/reaction.py

@@ -133,7 +133,7 @@ def burst_colors(self) -> list[Colour]:
         return self.burst_colours
 
     @property
-    def count_details(self):
+    def count_details(self) -> ReactionCountDetails:
         """Returns :class:`ReactionCountDetails` for the individual counts of normal and super reactions made."""
         return ReactionCountDetails(self._count_details)