fix mypy

Author: mykola-mokhnach

appium/webdriver/appium_service.py

@@ -127,7 +127,7 @@ def start(self, **kwargs: Any) -> sp.Popen:
             raise AppiumServiceError(error_msg)
         return self._process
 
-    def stop(self, timeout=5.5) -> bool:
+    def stop(self, timeout: float = 5.5) -> bool:
         """Stops Appium service if it is running.
 
         The call will be ignored if the service is not running