chore: use Signal.emit instead of emit_signal to avoid UNUSED_SIGNAL warning

[akien-mga]

Alternatively, the UNUSED_SIGNAL warning could be fully disabled.

Upstream bug report: godotengine/godot#89632

[akien-mga]

Actually this shouldn't be needed once godotengine/godot#89675 is merged and cherry-picked.

Another alternative would be the use Signal.emit instead of emit_signal. I'll update the PR to do that.

Edit: I was wrong, 89675 / changing one of the call to emit fixes one occurrence of the warning, but the second occurrence actually rightfully exposes a bug: the foot_step signal never seems to be emitted. And indeed I checked with some prints and play_foot_step_sound is never called during gameplay.

$ rg foot_step
Player/CharacterSkin.gd
4:signal foot_step

Player/Player.gd
235:func play_foot_step_sound() -> void:

Player/Player.tscn
270:[connection signal="foot_step" from="CharacterRotationRoot/CharacterSkin" to="." method="play_foot_step_sound"]

Opened a dedicated bug report for that: #42.

[NathanLovato]

Thanks!