[cleanup] Sort imports

Using https://github.com/PyCQA/isort

    isort -m VERTICAL_HANGING_INDENT --py 36 -l 80 --rr -n --tc .

yt_dlp/postprocessor/exec.py

@@ -2,11 +2,7 @@ import subprocess
 
 from .common import PostProcessor
 from ..compat import compat_shlex_quote
-from ..utils import (
-    encodeArgument,
-    PostProcessingError,
-    variadic,
-)
+from ..utils import PostProcessingError, encodeArgument, variadic
 
 
 class ExecPP(PostProcessor):