patch 8.2.1573: Vim9: getreg() does not take "true" as argument

Problem:    Vim9: getreg() does not take "true" as argument.
Solution:   Use tv_get_bool_chk().  (closes #6820)

src/version.c

@@ -754,6 +754,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1573,
 /**/
     1572,
 /**/