Apply Mac double buffering workaround for wxSTC correctly

The changes of bf418320b7 only modified
the generated file instead of modifying the file it's generated from, so
were lost during subsequent regenerations.

Fix this by back-propagating them to the correct place.

See #18085.

src/stc/stc.cpp.in

@@ -224,8 +224,9 @@ bool wxStyledTextCtrl::Create(wxWindow *parent,
     // STC doesn't support RTL languages at all
     SetLayoutDirection(wxLayout_LeftToRight);
 
-    // Rely on native double buffering by default.
-#if wxALWAYS_NATIVE_DOUBLE_BUFFER
+    // Rely on native double buffering by default, except under Mac where it
+    // doesn't work for some reason, see #18085.
+#if wxALWAYS_NATIVE_DOUBLE_BUFFER && !defined(__WXMAC__)
     SetBufferedDraw(false);
 #else
     SetBufferedDraw(true);