patch 8.2.1441: running tests in tiny version gives error for summarize.vim

Problem:    Running tests in tiny version gives error for summarize.vim.
Solution:   Set 'cpoptions' to allow for line continuation.  Restore
            redirecting test output to /dev/null.

src/testdir/summarize.vim

@@ -1,3 +1,4 @@
+set cpo&vim
 if 1
   " This is executed only with the eval feature
   set nocompatible