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_options.vim b/src/testdir/test_options.vim
index 9708fcc..1f71e1f 100644
--- a/src/testdir/test_options.vim
+++ b/src/testdir/test_options.vim
@@ -277,11 +277,11 @@
   set complete=.,w,b,u,k,\ s,i,d,],t,U,f,o
   call assert_fails('set complete=i^-10', 'E535:')
   call assert_fails('set complete=i^x', 'E535:')
-  call assert_fails('set complete=k^2,t^-1,s^', 'E535')
-  call assert_fails('set complete=t^-1', 'E535')
-  call assert_fails('set complete=kfoo^foo2', 'E535')
-  call assert_fails('set complete=kfoo^', 'E535')
-  call assert_fails('set complete=.^', 'E535')
+  call assert_fails('set complete=k^2,t^-1,s^', 'E535:')
+  call assert_fails('set complete=t^-1', 'E535:')
+  call assert_fails('set complete=kfoo^foo2', 'E535:')
+  call assert_fails('set complete=kfoo^', 'E535:')
+  call assert_fails('set complete=.^', 'E535:')
   set complete=.,w,b,u,k,s,i,d,],t,U,f,o
   set complete=.
   set complete=.^10,t^0