patch 8.0.0403: GUI tests may fail

Problem:    GUI tests may fail.
Solution:   Ignore the E285 error better. (Kazunobu Kuriyama)
diff --git a/src/testdir/test_gui_init.vim b/src/testdir/test_gui_init.vim
index a092299..811c6ec 100644
--- a/src/testdir/test_gui_init.vim
+++ b/src/testdir/test_gui_init.vim
@@ -15,7 +15,10 @@
   call GUITearDownCommon()
 endfunc
 
-" Make sure that the tests will be done with the GUI activated.
+" Ignore the "failed to create input context" error.
+call test_ignore_error('E285')
+
+" Start the GUI now, in the foreground.
 gui -f
 
 func Test_set_guiheadroom()