patch 8.2.3093: tablabel_tooltip test fails with Athena

Problem:    tablabel_tooltip test fails with Athena. (Dominique Pellé)
Solution:   Skip the test when using Athena. (closes #8508)
diff --git a/src/testdir/test_gui.vim b/src/testdir/test_gui.vim
index 762e332..b727372 100644
--- a/src/testdir/test_gui.vim
+++ b/src/testdir/test_gui.vim
@@ -1118,6 +1118,8 @@
 endfunc
 
 func Test_gui_tablabel_tooltip()
+  CheckNotFeature gui_athena
+
   %bw!
   " Removing the tabline at the end of this test, reduces the window height by
   " one. Save and restore it after the test.