patch 9.0.0106: illegal byte regexp test doesn't fail when fix is reversed

Problem:    Illegal byte regexp test doesn't fail when fix is reversed.
Solution:   Make sure illegal bytes end up in sourced script file.

src/testdir/test_regexp_utf8.vim

@@ -563,12 +563,8 @@ func Test_match_invalid_byte()
 endfunc
 
 func Test_match_illegal_byte()
-  let lines =<< trim END
+  " Text has illegal bytes which need to be set explicitly
-      silent! buffer ÿ\c
+  let lines = ["norm :set no\x01\<CR>", "silent n\xff", "silent norm :b\xff\<CR>"]
-      next ÿ
-      0scriptnames
-      source
-  END
   call writefile(lines, 'Xregexp')
   call system(GetVimCommand() .. ' -X -Z -e -s -S Xregexp -c qa!')
 

src/version.c

@@ -735,6 +735,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    106,
 /**/
     105,
 /**/