Fix beatmap panels locally handling mod and ruleset changes unnecessarily

[peppy]

The BeatmapDifficultyCache handles mod changes, so handling locally is unnecessary. By handling locally, it creates a visual issue when adjusting mods often. Test using Ctrl +/- at song select and observing that without this change, the star rating will flicker back to the default due to the local re-fetch.

Before:

osu.2025-08-27.at.09.33.29.mp4

After:

osu.2025-08-27.at.09.32.37.mp4

[bdach]

should also be applied to

osu/osu.Game/Screens/SelectV2/PanelBeatmap.cs

Lines 202 to 206 in ec21685

	ruleset.BindValueChanged(_ =>
	{
	computeStarRating();
	updateKeyCount();
	});

osu/osu.Game/Screens/SelectV2/PanelBeatmapStandalone.cs

Lines 212 to 222 in ec21685

	ruleset.BindValueChanged(_ =>
	{
	computeStarRating();
	updateKeyCount();
	});
	mods.BindValueChanged(_ =>
	{
	computeStarRating();
	updateKeyCount();
	}, true);