patch 9.1.0981: tests: typo in test_filetype.vim

Problem:  tests: typo in test_filetype.vim
Solution: fix comment, update lnkmap syntax file and add
          DESCT keyword
          (Wu, Zhenyu)

closes: #16348

Signed-off-by: Wu, Zhenyu <wuzhenyu@ustc.edu>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/version.c b/src/version.c
index 5f1649e..a8f0eea 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    981,
+/**/
     980,
 /**/
     979,