patch 8.2.4677: the Athena GUI support is outdated

Problem:    The Athena GUI support is outdated.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_startup.vim b/src/testdir/test_startup.vim
index 1c1e1c0..6926ba3 100644
--- a/src/testdir/test_startup.vim
+++ b/src/testdir/test_startup.vim
@@ -441,7 +441,7 @@
 " Test the -reverse and +reverse arguments (for GUI only).
 func Test_reverse()
   CheckCanRunGui
-  CheckAnyOf Feature:gui_gtk Feature:gui_motif Feature:gui_athena
+  CheckAnyOf Feature:gui_gtk Feature:gui_motif
 
   let after =<< trim [CODE]
     call writefile([&background], "Xtest_reverse")
@@ -462,7 +462,7 @@
 " Test the -background and -foreground arguments (for GUI only).
 func Test_background_foreground()
   CheckCanRunGui
-  CheckAnyOf Feature:gui_gtk Feature:gui_motif Feature:gui_athena
+  CheckAnyOf Feature:gui_gtk Feature:gui_motif
 
   " Is there a better way to check the effect of -background & -foreground
   " other than merely looking at &background (dark or light)?
@@ -489,7 +489,7 @@
 
   if has('gui_gtk')
     let font = 'Courier 14'
-  elseif has('gui_motif') || has('gui_athena')
+  elseif has('gui_motif')
     let font = '-misc-fixed-bold-*'
   else
     throw 'Skipped: test does not set a valid font for this GUI'
@@ -511,10 +511,10 @@
 " Test the -geometry argument (for GUI only).
 func Test_geometry()
   CheckCanRunGui
-  CheckAnyOf Feature:gui_gtk Feature:gui_motif Feature:gui_athena
+  CheckAnyOf Feature:gui_gtk Feature:gui_motif
 
-  if has('gui_motif') || has('gui_athena')
-    " FIXME: With GUI Athena or Motif, the value of getwinposx(),
+  if has('gui_motif')
+    " FIXME: With GUI Motif the value of getwinposx(),
     "        getwinposy() and getwinpos() do not match exactly the
     "        value given in -geometry. Why?
     "        So only check &columns and &lines for those GUIs.
@@ -550,7 +550,7 @@
 " Test the -iconic argument (for GUI only).
 func Test_iconic()
   CheckCanRunGui
-  CheckAnyOf Feature:gui_gtk Feature:gui_motif Feature:gui_athena
+  CheckAnyOf Feature:gui_gtk Feature:gui_motif
 
   call RunVim([], [], '-f -g -iconic -cq')