patch 8.2.2242: Vim9: bar line continuation does not work at script level

Problem:    Vim9: line continuation with bar does not work at script level.
Solution:   Check for Vim9 script.
diff --git a/src/structs.h b/src/structs.h
index ba42e33..102be0e 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -1565,8 +1565,8 @@
 // type of getline() last argument
 typedef enum {
     GETLINE_NONE,	    // do not concatenate any lines
-    GETLINE_CONCAT_CONT,    // concatenate continuation lines in Vim9 script
-    GETLINE_CONCAT_CONTDEF, // concatenate continuation lines always
+    GETLINE_CONCAT_CONT,    // concatenate continuation lines with backslash
+    GETLINE_CONCAT_CONTBAR, // concatenate continuation lines with \ and |
     GETLINE_CONCAT_ALL	    // concatenate continuation and Vim9 # comment lines
 } getline_opt_T;