patch 9.0.0828: various typos

Problem:    Various typos.
Solution:   Correct typos. (closes #11432)
diff --git a/src/highlight.c b/src/highlight.c
index d0d6fde..f937e08 100644
--- a/src/highlight.c
+++ b/src/highlight.c
@@ -634,7 +634,7 @@
 /*
  * Link highlight group 'from_hg' to 'to_hg'.
  * 'dodefault' is set to TRUE for ":highlight default link".
- * 'forceit' is set to TRUE for ":higlight! link"
+ * 'forceit' is set to TRUE for ":highlight! link"
  * 'init' is set to TRUE when initializing all the highlight groups.
  */
     static void