patch 8.2.3474: some places use "Vimscript" instead of "Vim script"

Problem:    Some places use "Vimscript" instead of "Vim script".
Solution:   Consistently use "Vim script". (Hirohito Higashi, closes #8910)
diff --git a/src/getchar.c b/src/getchar.c
index 2d31c03..93e3b87 100644
--- a/src/getchar.c
+++ b/src/getchar.c
@@ -2182,7 +2182,7 @@
 /*
  * Process messages that have been queued for netbeans or clientserver.
  * Also check if any jobs have ended.
- * These functions can call arbitrary vimscript and should only be called when
+ * These functions can call arbitrary Vim script and should only be called when
  * it is safe to do so.
  */
     void