refactor: Use with in Accelerator.autocast()instead of __enter__() and __exit__() for more elegant style. (#3767)

* refactor: Use ` with`  in `Accelerator.autocast()`instead of  `__enter__()` and `__exit__()`for more elegant style.

* Apply style fixes

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Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

Author: EquationWalker

src/accelerate/accelerator.py

@@ -21,7 +21,6 @@
 import os
 import re
 import shutil
-import sys
 import warnings
 from collections import OrderedDict
 from contextlib import contextmanager
@@ -4069,10 +4068,8 @@ def autocast(self, autocast_handler: AutocastKwargs = None):
         if autocast_handler is None:
             autocast_handler = self.autocast_handler
         autocast_context = get_mixed_precision_context_manager(self.native_amp, autocast_handler)
-        autocast_context.__enter__()
-        # TODO: should the `yield` be in a try/finally block?
-        yield
-        autocast_context.__exit__(*sys.exc_info())
+        with autocast_context:
+            yield
 
     @contextmanager
     def profile(self, profile_handler: ProfileKwargs | None = None):