Upgrade mypy to 0.730, address raised issues (#26959)

https://mypy-lang.blogspot.com/2019/09/mypy-730-released.html

homeassistant/util/location.py

@@ -6,7 +6,7 @@ detect_location_info and elevation are mocked by default during tests.
 import asyncio
 import collections
 import math
-from typing import Any, Optional, Tuple, Dict
+from typing import Any, Optional, Tuple, Dict, cast
 
 import aiohttp
 
@@ -159,7 +159,7 @@ def vincenty(
     if miles:
         s *= MILES_PER_KILOMETER  # kilometers to miles
 
-    return round(s, 6)
+    return round(cast(float, s), 6)
 
 
 async def _get_ipapi(session: aiohttp.ClientSession) -> Optional[Dict[str, Any]]: