patch 8.1.1829: difference in screenshots

Problem:    Difference in screenshots.
Solution:   Update screenshots.  Change checks in a few more tests.
            (closes #4789)
diff --git a/src/testdir/test_balloon_gui.vim b/src/testdir/test_balloon_gui.vim
index fd01309..5b486c0 100644
--- a/src/testdir/test_balloon_gui.vim
+++ b/src/testdir/test_balloon_gui.vim
@@ -1,10 +1,7 @@
 " Tests for 'ballooneval' in the GUI.
 
-if !has('gui_running')
-  throw 'Skipped: only works in the GUI'
-endif
-
 source check.vim
+CheckGui
 CheckFeature balloon_eval
 
 func Test_balloon_show_gui()