### Godot version

v4.0.beta17.official [c40020513]

### System information

Windows 11, OpenGL (Compatibility), RTX 2060 (31.0.15.2824)

### Issue description

I tried to make a blurred panel for a ui element with texturelod via shader:

```glsl
shader_type canvas_item;

uniform sampler2D SCREEN_TEXTURE : hint_screen_texture, filter_linear_mipmap_anisotropic;
uniform float blur_amount : hint_range(0.0, 5.0);

void fragment() {
	vec4 blurred = textureLod(SCREEN_TEXTURE, SCREEN_UV, blur_amount);
	COLOR = blurred;
}
```

but what I got instead is this:
![image](https://user-images.githubusercontent.com/72286622/217170426-49f6712d-47ef-4c53-b9f1-30d8ad868084.png)

vulkan renderer does not exhibit this issue:
![image](https://user-images.githubusercontent.com/72286622/217170565-a013c712-94f6-49d1-b9ec-091c28a7790b.png)


### Steps to reproduce

1. Add a TextureRect node
2. Add a Panel node to overlay the previously added node
3. Apply the blur shader to the panel node

### Minimal reproduction project

N/A
Size2i margin;
	int scale;
	switch (rt->sdf_oversize) {
		case RS::VIEWPORT_SDF_OVERSIZE_100_PERCENT: {
			scale = 100;
		} break;
		case RS::VIEWPORT_SDF_OVERSIZE_120_PERCENT: {
			scale = 120;
		} break;
		case RS::VIEWPORT_SDF_OVERSIZE_150_PERCENT: {
			scale = 150;
		} break;
		case RS::VIEWPORT_SDF_OVERSIZE_200_PERCENT: {
			scale = 200;
		} break;
		default: {
		}
	}
	margin = (rt->size * scale / 100) - rt->size;
	Rect2i r(Vector2i(), rt->size);
	r.position -= margin;
	r.size += margin * 2;
	return r;
}
Rect2i TextureStorage::render_target_get_sdf_rect(RID p_render_target) const {