Fix bug in 6d916fe709 (#4219)

Update only to legacy version on old MacOS

Authored by: StefanLobbenmeier

yt_dlp/update.py

@@ -25,6 +25,8 @@ def _get_variant_and_executable_path():
             return 'py2exe', path
         if sys._MEIPASS == os.path.dirname(path):
             return f'{sys.platform}_dir', path
+        if sys.platform == 'darwin' and version_tuple(platform.mac_ver()[0]) < (10, 15):
+            return 'darwin_legacy_exe', path
         return f'{sys.platform}_exe', path
 
     path = os.path.dirname(__file__)
@@ -45,6 +47,7 @@ _FILE_SUFFIXES = {
     'py2exe': '_min.exe',
     'win32_exe': '.exe',
     'darwin_exe': '_macos',
+    'darwin_legacy_exe': '_macos_legacy',
     'linux_exe': '_linux',
 }