patch 8.2.0058: running tests changes ~/.viminfo

Problem:    Running tests changes ~/.viminfo.
Solution:   Make 'viminfo' empty when summarizing tests results. (closes #5414)

src/testdir/summarize.vim

@@ -1,6 +1,7 @@
 if 1
   " This is executed only with the eval feature
   set nocompatible
+  set viminfo=
   func Count(match, type)
     if a:type ==# 'executed'
       let g:executed += (a:match+0)