[cleanup] Sort imports

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

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

yt_dlp/downloader/rtmp.py

@@ -6,11 +6,11 @@ import time
 from .common import FileDownloader
 from ..compat import compat_str
 from ..utils import (
-    check_executable,
-    encodeFilename,
-    encodeArgument,
-    get_exe_version,
     Popen,
+    check_executable,
+    encodeArgument,
+    encodeFilename,
+    get_exe_version,
 )