patch 8.2.4677: the Athena GUI support is outdated

Problem:    The Athena GUI support is outdated.
Solution:   Remove the Athena GUI code.
diff --git a/src/testdir/test_edit.vim b/src/testdir/test_edit.vim
index e3518d8..a96a95b 100644
--- a/src/testdir/test_edit.vim
+++ b/src/testdir/test_edit.vim
@@ -2094,7 +2094,7 @@
 func Test_edit_CTRL_hat()
   CheckFeature xim
 
-  " FIXME: test fails with Athena and Motif GUI.
+  " FIXME: test fails with Motif GUI.
   "        test also fails when running in the GUI.
   CheckFeature gui_gtk
   CheckNotGui