patch 8.2.4918: conceal character from matchadd() displayed too many times

Problem:    Conceal character from matchadd() displayed too many times.
Solution:   Check the syntax flag. (closes #10381, closes #7268)
diff --git a/src/version.c b/src/version.c
index 29cddd5..f949dd6 100644
--- a/src/version.c
+++ b/src/version.c
@@ -747,6 +747,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    4918,
+/**/
     4917,
 /**/
     4916,