Fix AnimatedWalkingSprite.update_animation clobbering scale_y

[uttam12331]

Summary

AnimatedWalkingSprite.update_animation sizes the sprite from the texture, but the height line uses scale_x instead of scale_y:

self.width  = self._texture.width  * self.scale_x
self.height = self._texture.height * self.scale_x   # should be scale_y

The inherited height setter derives scale_y from the value assigned (self._scale = self._scale[0], value / self._texture.height), so assigning texture.height * scale_x forces scale_y := scale_x. Every animation update therefore both mis-sizes the sprite and silently corrupts a non-uniform scale.

Repro (arcade 3.3.3):

tex = arcade.Texture.create_empty("t", (10, 20))
spr = arcade.AnimatedWalkingSprite(scale=(2.0, 3.0))
spr.stand_right_textures = [tex]; spr.texture = tex
spr.change_x = spr.change_y = 0
spr.update_animation()
# before: spr.scale == (2.0, 2.0), spr.height == 40.0   <- scale_y clobbered 3.0 -> 2.0
# after:  spr.scale == (2.0, 3.0), spr.height == 60.0

Fix

Use scale_y for the height. The width line one above already correctly uses scale_x, matching the base-class texture setters (sprite/base.py, sprite/sprite.py) which use _scale[0] for width and _scale[1] for height.

self.height = self._texture.height * self.scale_y

Test

Added test_update_animation_preserves_scale_y in tests/unit/sprite/test_sprite_animated_walking.py — it constructs an AnimatedWalkingSprite(scale=(2.0, 3.0)), runs update_animation, and asserts the scale and dimensions are preserved. It fails on development (scale becomes (2.0, 2.0), height 40.0) and passes with this change. ruff format --check clean and the change adds no new ruff check findings.

AnimatedWalkingSprite is soft-deprecated in its docstring, but it is still exported in arcade.__all__ and is the sprite used in the platformer tutorial (platformer_part_twelve), so the silent scale corruption still affects users following the docs.