vim-patch:8.1.0907: CI tests on AppVeyor are failing

Problem:    CI tests on AppVeyor are failing.
Solution:   Reduce the recursiveness limit for regexp.
5382f12c91

src/nvim/regexp_nfa.c

@@ -3961,7 +3961,7 @@ addstate (
 
   // This function is called recursively.  When the depth is too much we run
   // out of stack and crash, limit recursiveness here.
-  if (++depth >= 10000 || subs == NULL) {
+  if (++depth >= 5000 || subs == NULL) {
     depth--;
     return NULL;
   }