fix(typing): Add more typing info to Scope.update_from_kwargs's "contexts" (#4080)

The original type hint could be understood as a one-level `dict` of `str` to `Any`, when in fact, it's a two-level dict.

Author: Perlence

Diff for: sentry_sdk/scope.py

@@ -1568,7 +1568,7 @@ def update_from_kwargs(
         user=None,  # type: Optional[Any]
         level=None,  # type: Optional[LogLevelStr]
         extras=None,  # type: Optional[Dict[str, Any]]
-        contexts=None,  # type: Optional[Dict[str, Any]]
+        contexts=None,  # type: Optional[Dict[str, Dict[str, Any]]]
         tags=None,  # type: Optional[Dict[str, str]]
         fingerprint=None,  # type: Optional[List[str]]
     ):