Kill fe_set_hilight()

It just duplicates functionality and this fixes:

- alert_taskbar chanopt not being respected
- tab color being incorrect when highlight print events are eaten

src/fe-text/fe-text.c

@@ -618,10 +618,6 @@ fe_cleanup (void)
 {
 }
 void
-fe_set_hilight (struct session *sess)
-{
-}
-void
 fe_set_tab_color (struct session *sess, int col)
 {
 }