remove 2.2 and 2.6 compat code (closes #22200)

Patch from Thomas Kluyver.

command/install.py

@@ -15,32 +15,17 @@ from distutils.util import convert_path, subst_vars, change_root
 from distutils.util import get_platform
 from distutils.errors import DistutilsOptionError
 
-# this keeps compatibility from 2.3 to 2.5
-if sys.version < "2.6":
-    USER_BASE = None
-    USER_SITE = None
-    HAS_USER_SITE = False
-else:
-    from site import USER_BASE
-    from site import USER_SITE
-    HAS_USER_SITE = True
-
-if sys.version < "2.2":
-    WINDOWS_SCHEME = {
-        'purelib': '$base',
-        'platlib': '$base',
-        'headers': '$base/Include/$dist_name',
-        'scripts': '$base/Scripts',
-        'data'   : '$base',
-    }
-else:
-    WINDOWS_SCHEME = {
-        'purelib': '$base/Lib/site-packages',
-        'platlib': '$base/Lib/site-packages',
-        'headers': '$base/Include/$dist_name',
-        'scripts': '$base/Scripts',
-        'data'   : '$base',
-    }
+from site import USER_BASE
+from site import USER_SITE
+HAS_USER_SITE = True
+
+WINDOWS_SCHEME = {
+    'purelib': '$base/Lib/site-packages',
+    'platlib': '$base/Lib/site-packages',
+    'headers': '$base/Include/$dist_name',
+    'scripts': '$base/Scripts',
+    'data'   : '$base',
+}
 
 INSTALL_SCHEMES = {
     'unix_prefix': {