patch 8.2.1190: Vim9: checking for Vim9 syntax is spread out

Problem:    Vim9: checking for Vim9 syntax is spread out.
Solution:   Use in_vim9script().
diff --git a/src/dict.c b/src/dict.c
index a549ed7..eedaf42 100644
--- a/src/dict.c
+++ b/src/dict.c
@@ -803,7 +803,7 @@
     dictitem_T	*item;
     char_u	*start = skipwhite(*arg + 1);
     char_u	buf[NUMBUFLEN];
-    int		vim9script = current_sctx.sc_version == SCRIPT_VERSION_VIM9;
+    int		vim9script = in_vim9script();
     int		had_comma;
 
     /*