Added count argument to spop (#3786)

* Added `count` argument to `spop`

* Fixed default value

third_party/2and3/redis/client.pyi

@@ -200,7 +200,7 @@ class Redis(object):
     def sismember(self, name, value): ...
     def smembers(self, name): ...
     def smove(self, src, dst, value): ...
-    def spop(self, name): ...
+    def spop(self, name, count: Optional[int] = ...): ...
     def srandmember(self, name, number=...): ...
     def srem(self, name, *values): ...
     def sunion(self, keys, *args): ...