patch 9.1.0915: GVim: default font size a bit too small

Problem:  GVim: default font size a bit too small
Solution: increase guifont size to 12 pt on GTK builds
          of gVim (matveyt).

fixes: #16172
closes: #16178

Signed-off-by: matveyt <matthewtarasov@yandex.ru>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/testdir/test_highlight.vim b/src/testdir/test_highlight.vim
index 9bc5f12..5189b61 100644
--- a/src/testdir/test_highlight.vim
+++ b/src/testdir/test_highlight.vim
@@ -781,8 +781,8 @@
   if !has('gui_running')
     call assert_match('hi Normal\s*clear', hlNormal)
   elseif has('gui_gtk2') || has('gui_gnome') || has('gui_gtk3')
-    " expect is DEFAULT_FONT of gui_gtk_x11.c
-    call assert_match('hi Normal\s*font=Monospace 10', hlNormal)
+    " expect is DEFAULT_FONT of gui_gtk_x11.c (any size)
+    call assert_match('hi Normal\s*font=Monospace\>', hlNormal)
   elseif has('gui_motif')
     " expect is DEFAULT_FONT of gui_x11.c
     call assert_match('hi Normal\s*font=7x13', hlNormal)