patch 8.1.2393: using old C style comments

Problem:    Using old C style comments.
Solution:   Use // comments where appropriate.
diff --git a/src/version.c b/src/version.c
index 93dc2a1..c571e6c 100644
--- a/src/version.c
+++ b/src/version.c
@@ -743,6 +743,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2393,
+/**/
     2392,
 /**/
     2391,