sleep: don't complain about missing dbus-next

[tych0]

This originally started as a patch that looked like this:

diff --git a/libqtile/hook.py b/libqtile/hook.py
index c3df2d16..8640cb8d 100644
--- a/libqtile/hook.py
+++ b/libqtile/hook.py
@@ -192,6 +192,9 @@ class Registry:
             except:  # noqa: E722
                 logger.exception("Error in hook %s", event)

+    def has_hook(self, event):
+        return len(subscriptions[self.name].get(event, [])) > 0
+

 hooks: list[Hook] = [
     Hook(
@@ -1032,3 +1035,4 @@ qtile_hooks = Registry("qtile", hooks)
 subscribe = qtile_hooks.subscribe
 unsubscribe = qtile_hooks.unsubscribe
 fire = qtile_hooks.fire
+has_hook = qtile_hooks.has_hook
diff --git a/libqtile/resources/sleep.py b/libqtile/resources/sleep.py
index 5038b93d..7618f3be 100644
--- a/libqtile/resources/sleep.py
+++ b/libqtile/resources/sleep.py
@@ -82,7 +82,7 @@ class Inhibitor:
         Will create connection to dbus only if we want to listen out
         for a sleep or wake signal.
         """
-        if not has_dbus:
+        if not has_dbus and any(map(hook.has_hook, ["suspend", "resume"])):
             logger.warning("dbus-next is not installed. Cannot run inhibitor process.")
             return

but then when testing it, I realized this functionality already exists, via wants_sleep(), which does:

2024-02-24 08:51:07,524 WARNING libqtile sleep.py:want_sleep():L68 dbus-next must be installed to listen to sleep signals

So let's just drop this message entirely, since it's a duplicate warning in the case where users have hooks installed, and it's a spurious warning in the case when they don't.

[elParaguayo]

Looks good.