patch 8.2.4858: K_SPECIAL may be escaped twice

Problem:    K_SPECIAL may be escaped twice.
Solution:   Avoid double escaping. (closes #10340)
diff --git a/src/highlight.c b/src/highlight.c
index 6a2b087..1e6f9c7 100644
--- a/src/highlight.c
+++ b/src/highlight.c
@@ -1356,7 +1356,7 @@
 	// Copy characters from arg[] to buf[], translating <> codes.
 	for (p = arg, off = 0; off < 100 - 6 && *p; )
 	{
-	    len = trans_special(&p, buf + off, FSK_SIMPLIFY, NULL);
+	    len = trans_special(&p, buf + off, FSK_SIMPLIFY, FALSE, NULL);
 	    if (len > 0)	    // recognized special char
 		off += len;
 	    else		    // copy as normal char