Remove traces of Mac OS 9 support, again (#9508).

This was done in r80805 (#7908) and erroneously brought back by the
distutils revert.  This commit removes more code than the original,
which was uncomplete.  There is no NEWS entry, like in r80805.

Lib/distutils/command/install.py

@@ -60,14 +60,6 @@ INSTALL_SCHEMES = {
         'data'   : '$base',
         },
     'nt': WINDOWS_SCHEME,
-    'mac': {
-        'purelib': '$base/Lib/site-packages',
-        'platlib': '$base/Lib/site-packages',
-        'headers': '$base/Include/$dist_name',
-        'scripts': '$base/Scripts',
-        'data'   : '$base',
-        },
-
     'os2': {
         'purelib': '$base/Lib/site-packages',
         'platlib': '$base/Lib/site-packages',
@@ -95,14 +87,6 @@ if HAS_USER_SITE:
         'data'   : '$userbase',
         }
 
-    INSTALL_SCHEMES['mac_user'] = {
-        'purelib': '$usersite',
-        'platlib': '$usersite',
-        'headers': '$userbase/$py_version_short/include/$dist_name',
-        'scripts': '$userbase/bin',
-        'data'   : '$userbase',
-        }
-
     INSTALL_SCHEMES['os2_home'] = {
         'purelib': '$usersite',
         'platlib': '$usersite',