bpo-35213: Where appropriate, use 'macOS' in idlelib. (#10478)


diff --git a/Lib/idlelib/config.py b/Lib/idlelib/config.py
index 0eb90fc..79d988f 100644
--- a/Lib/idlelib/config.py
+++ b/Lib/idlelib/config.py
@@ -562,12 +562,11 @@
         result = self.GetKeySet(self.CurrentKeys())
 
         if sys.platform == "darwin":
-            # OS X Tk variants do not support the "Alt" keyboard modifier.
-            # So replace all keybingings that use "Alt" with ones that
-            # use the "Option" keyboard modifier.
-            # TODO (Ned?): the "Option" modifier does not work properly for
-            #        Cocoa Tk and XQuartz Tk so we should not use it
-            #        in default OS X KeySets.
+            # macOS (OS X) Tk variants do not support the "Alt"
+            # keyboard modifier.  Replace it with "Option".
+            # TODO (Ned?): the "Option" modifier does not work properly
+            #     for Cocoa Tk and XQuartz Tk so we should not use it
+            #     in the default 'OSX' keyset.
             for k, v in result.items():
                 v2 = [ x.replace('<Alt-', '<Option-') for x in v ]
                 if v != v2: