Issue #24710: Use cls in TracebackException.from_exception.

Minor cleanup patch from Berker Peksag.

Lib/traceback.py

@@ -477,10 +477,9 @@ class TracebackException:
             self._load_lines()
 
     @classmethod
-    def from_exception(self, exc, *args, **kwargs):
+    def from_exception(cls, exc, *args, **kwargs):
         """Create a TracebackException from an exception."""
-        return TracebackException(
-            type(exc), exc, exc.__traceback__, *args, **kwargs)
+        return cls(type(exc), exc, exc.__traceback__, *args, **kwargs)
 
     def _load_lines(self):
         """Private API. force all lines in the stack to be loaded."""