term: drop term->render.title.is_armed

This boolean isn't needed. The idea was probably to not re-program the
timer unnecessarily, or even to prevent it from being moved forward in
time indefinitely.

However, the logic has (probably) gone through some changes, that now
makes it irrelevant.

The timer isn't moved forward indefinitely; it is always set to 8ms
from the last title update. The closer we get to that point in time,
the smaller the timeout we set.

Now, is_armed _did_ prevent the timer from being re-programmed. But
that tiny performance tweak isn't really necessary, as the title
should, in normal cases, not be set that often anyway.

render.c

@@ -4508,9 +4508,6 @@ fdm_hook_refresh_pending_terminals(struct fdm *fdm, void *data)
 void
 render_refresh_title(struct terminal *term)
 {
-    if (term->render.title.is_armed)
-        return;
-
     struct timespec now;
     if (clock_gettime(CLOCK_MONOTONIC, &now) < 0)
         return;