Use Literal instead of int for logging levels (#6610)

stdlib/logging/__init__.pyi

@@ -244,14 +244,14 @@ class Logger(Filterer):
     def hasHandlers(self) -> bool: ...
     def callHandlers(self, record: LogRecord) -> None: ...  # undocumented
 
-CRITICAL: int
-FATAL: int
-ERROR: int
-WARNING: int
-WARN: int
-INFO: int
-DEBUG: int
-NOTSET: int
+CRITICAL: Literal[50]
+FATAL: Literal[50]
+ERROR: Literal[40]
+WARNING: Literal[30]
+WARN: Literal[30]
+INFO: Literal[20]
+DEBUG: Literal[10]
+NOTSET: Literal[0]
 
 class Handler(Filterer):
     level: int  # undocumented