### Godot version

3.5.1 custom build

### System information

N/A

### Issue description

When using Line2D, I noticed a discrepancy with UVs depending on the end cap mode.

Here are some examples using a tiled repeating texture:

### No capping ✔️ 
![image](https://user-images.githubusercontent.com/95356449/218230984-e5d507d4-7af7-4967-aee7-79c8daa206ff.png)

### Begin cap: Box ✔️ 
![image](https://user-images.githubusercontent.com/95356449/218231092-311370cc-7ff8-4699-976b-c4581eaada0a.png)

### End cap: Box ❌ 
![image](https://user-images.githubusercontent.com/95356449/218231131-00ddf4f7-2a9a-4740-a445-a8601ab026e1.png)


### Steps to reproduce

Create a Line2D
Add a texture with repeating enabled
Set end cap mode to Box

### Minimal reproduction project

not needed, bugfix pr incoming
Orientation opposite_orientation = orientation == UP ? DOWN : UP;
	Vector2 vbegin = vertices[_last_index[opposite_orientation]] - center;
	float radius = vbegin.length();
	float angle_step = Math_PI / static_cast<float>(round_precision);
	float steps = Math::abs(angle_delta) / angle_step;
	if (angle_delta < 0.f) {
		angle_step = -angle_step;
	}
	float t = Vector2(1, 0).angle_to(vbegin);
	float end_angle = t + angle_delta;
	Vector2 rpos(0, 0);
	
	for (int ti = 0; ti < steps; ++ti, t += angle_step) {
		rpos = center + Vector2(Math::cos(t), Math::sin(t)) * radius;
		strip_add_tri(rpos, orientation);
	}
	
	rpos = center + Vector2(Math::cos(end_angle), Math::sin(end_angle)) * radius;
	strip_add_tri(rpos, orientation);
}
void LineBuilder::new_arc(Vector2 center, Vector2 vbegin, float angle_delta, Color color, Rect2 uv_rect) {