patch 9.1.1325: tests: not checking error numbers properly

Problem:  tests: not checking error numbers properly.
Solution: Add a trailing comma to avoid matching a different error
          number with the same prefix (zeertzjq)

closes: #17159

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/testdir/test_arglist.vim b/src/testdir/test_arglist.vim
index d21a222..c320d09 100644
--- a/src/testdir/test_arglist.vim
+++ b/src/testdir/test_arglist.vim
@@ -640,7 +640,7 @@
 func Test_clear_arglist_in_all()
   n 0 00 000 0000 00000 000000
   au WinNew 0 n 0
-  call assert_fails("all", "E1156")
+  call assert_fails("all", "E1156:")
   au! *
 endfunc