patch 8.2.1422: the Mac GUI implementation is outdated

Problem:    The Mac GUI implementation is outdated and probably doesn't even
            work.
Solution:   Remove the Mac GUI code.  The MacVim project provides the
            supported Vim GUI version.
diff --git a/src/evalfunc.c b/src/evalfunc.c
index 5607ef9..bbc3404 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -3920,13 +3920,7 @@
 		0
 #endif
 		},
-	{"gui_mac",
-#ifdef FEAT_GUI_MAC
-		1
-#else
-		0
-#endif
-		},
+	{"gui_mac", 0},
 	{"gui_motif",
 #ifdef FEAT_GUI_MOTIF
 		1