patch 8.2.2262: Vim9: converting bool to string prefixes v:

Problem:    Vim9: converting bool to string prefixes v:.
Solution:   Do not use the v: prefix.
diff --git a/src/evalvars.c b/src/evalvars.c
index f9b3c48..9f84d76 100644
--- a/src/evalvars.c
+++ b/src/evalvars.c
@@ -2068,8 +2068,8 @@
 {
     switch (nr)
     {
-	case VVAL_FALSE: return "v:false";
-	case VVAL_TRUE:  return "v:true";
+	case VVAL_FALSE: return in_vim9script() ? "false" : "v:false";
+	case VVAL_TRUE:  return in_vim9script() ? "true" : "v:true";
 	case VVAL_NONE:  return "v:none";
 	case VVAL_NULL:  return "v:null";
     }