patch 8.2.4684: cannot open a channel on a Unix domain socket

Problem:    Cannot open a channel on a Unix domain socket.
Solution:   Add Unix domain socket support. (closes #10062)
diff --git a/src/testdir/test_cmdline.vim b/src/testdir/test_cmdline.vim
index e38a569..8034bdb 100644
--- a/src/testdir/test_cmdline.vim
+++ b/src/testdir/test_cmdline.vim
@@ -620,8 +620,8 @@
         \ ':5s':        'substitute',
         \ "'<,'>s":     'substitute',
         \ ":'<,'>s":    'substitute',
-        \ 'CheckUni':   'CheckUnix',
-        \ 'CheckUnix':  'CheckUnix',
+        \ 'CheckLin':   'CheckLinux',
+        \ 'CheckLinux': 'CheckLinux',
   \ }
 
   for [in, want] in items(tests)