patch 8.2.4307: a few more messages should not be translated

Problem:    A few more messages should not be translated.
Solution:   Remove _().
diff --git a/src/syntax.c b/src/syntax.c
index f1c844f..11f5587 100644
--- a/src/syntax.c
+++ b/src/syntax.c
@@ -3329,9 +3329,9 @@
     if (*arg == NUL)
     {
 	if (curwin->w_s->b_syn_conceal)
-	    msg(_("syntax conceal on"));
+	    msg("syntax conceal on");
 	else
-	    msg(_("syntax conceal off"));
+	    msg("syntax conceal off");
     }
     else if (STRNICMP(arg, "on", 2) == 0 && next - arg == 2)
 	curwin->w_s->b_syn_conceal = TRUE;
@@ -3359,9 +3359,9 @@
     if (*arg == NUL)
     {
 	if (curwin->w_s->b_syn_ic)
-	    msg(_("syntax case ignore"));
+	    msg("syntax case ignore");
 	else
-	    msg(_("syntax case match"));
+	    msg("syntax case match");
     }
     else if (STRNICMP(arg, "match", 5) == 0 && next - arg == 5)
 	curwin->w_s->b_syn_ic = FALSE;
@@ -3471,7 +3471,7 @@
 	msg_puts("\n");
 	if (curwin->w_s->b_syn_isk != empty_option)
 	{
-	    msg_puts(_("syntax iskeyword "));
+	    msg_puts("syntax iskeyword ");
 	    msg_outtrans(curwin->w_s->b_syn_isk);
 	}
 	else