patch 8.2.3140: MS-Windows: ipv6 channel test is very flaky also without GUI

Problem:    MS-Windows: ipv6 channel test is very flaky also without the GUI.
Solution:   Skip the test also without the GUI.
diff --git a/src/testdir/test_channel.vim b/src/testdir/test_channel.vim
index f88cba0..f2c0d17 100644
--- a/src/testdir/test_channel.vim
+++ b/src/testdir/test_channel.vim
@@ -253,9 +253,9 @@
 func Test_communicate_ipv6()
   CheckIPv6
 
-  " FIXME: this test is very flaky on MS-Windows with the GUI
-  if has('gui_running') && has('win32')
-    throw 'Skipped: test is very flaky with MS-Windows in GUI'
+  " FIXME: this test is very flaky on MS-Windows
+  if has('win32')
+    throw 'Skipped: test is very flaky with MS-Windows'
   endif
 
   call Test_communicate()