patch 8.0.1535: C syntax test still fails when using gvim

Problem:    C syntax test still fails when using gvim.
Solution:   Clear Normal cterm highlighting instead of setting it.
diff --git a/src/version.c b/src/version.c
index 085e0f9..5d8eb5a 100644
--- a/src/version.c
+++ b/src/version.c
@@ -779,6 +779,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1535,
+/**/
     1534,
 /**/
     1533,