[cleanup] Sort imports

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

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

yt_dlp/postprocessor/__init__.py

@@ -1,27 +1,25 @@
 # flake8: noqa: F401
 
-from ..utils import load_plugins
-
 from .common import PostProcessor
 from .embedthumbnail import EmbedThumbnailPP
-from .exec import ExecPP, ExecAfterDownloadPP
+from .exec import ExecAfterDownloadPP, ExecPP
 from .ffmpeg import (
-    FFmpegPostProcessor,
-    FFmpegCopyStreamPP,
     FFmpegConcatPP,
+    FFmpegCopyStreamPP,
     FFmpegEmbedSubtitlePP,
     FFmpegExtractAudioPP,
     FFmpegFixupDuplicateMoovPP,
     FFmpegFixupDurationPP,
-    FFmpegFixupStretchedPP,
-    FFmpegFixupTimestampPP,
     FFmpegFixupM3u8PP,
     FFmpegFixupM4aPP,
+    FFmpegFixupStretchedPP,
+    FFmpegFixupTimestampPP,
     FFmpegMergerPP,
     FFmpegMetadataPP,
+    FFmpegPostProcessor,
+    FFmpegSplitChaptersPP,
     FFmpegSubtitlesConvertorPP,
     FFmpegThumbnailsConvertorPP,
-    FFmpegSplitChaptersPP,
     FFmpegVideoConvertorPP,
     FFmpegVideoRemuxerPP,
 )
@@ -35,6 +33,7 @@ from .movefilesafterdownload import MoveFilesAfterDownloadPP
 from .sponskrub import SponSkrubPP
 from .sponsorblock import SponsorBlockPP
 from .xattrpp import XAttrMetadataPP
+from ..utils import load_plugins
 
 _PLUGIN_CLASSES = load_plugins('postprocessor', 'PP', globals())