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/scriptfile.c b/src/scriptfile.c
index ce4bafa..4e7df4d 100644
--- a/src/scriptfile.c
+++ b/src/scriptfile.c
@@ -1876,7 +1876,7 @@
 	emsg(_("E984: :scriptversion used outside of a sourced file"));
 	return;
     }
-    if (current_sctx.sc_version == SCRIPT_VERSION_VIM9)
+    if (in_vim9script())
     {
 	emsg(_("E1040: Cannot use :scriptversion after :vim9script"));
 	return;