patch 8.2.2138: Vim9: "exit_cb" causes Vim to exit

Problem:    Vim9: "exit_cb" causes Vim to exit.
Solution:   Require white space after a command in Vim9 script. (closes #7467)
            Also fix that Vim9 style heredoc was not always recognized.

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2138,
 /**/
     2137,
 /**/