Regression from #71248:

I believe this pull may have caused errors on WebGL since it moves the `GLES_OVER_GL` guard. WebGL does not support texture swizzling per: https://registry.khronos.org/webgl/specs/latest/2.0/#5.19
so this is causing the following trace in Chrome:
```
WebGL: INVALID_ENUM: texParameter: invalid parameter name
```
and it quickly fills up the 256 log limit for the same message in WebGL.

This doesn't appear to be breaking anything asides from causing the numerous log messages.

_Originally posted by @jnlopar in https://github.com/godotengine/godot/issues/71248#issuecomment-1384768973_

CC @rsjtdrjgfuzkfg @clayjohn
CopyEffects *copy_effects = CopyEffects::get_singleton();
	RenderTarget *rt = render_target_owner.get_or_null(p_render_target);
	ERR_FAIL_COND(!rt);
	ERR_FAIL_COND(rt->sdf_texture_write_fb == 0);
	Rect2i r = _render_target_get_sdf_rect(rt);
	Size2i size = r.size;
	int32_t shift = 0;
	bool shrink = false;
	switch (rt->sdf_scale) {
		case RS::VIEWPORT_SDF_SCALE_50_PERCENT: {
			size[0] >>= 1;
			size[1] >>= 1;
			shift = 1;
			shrink = true;
		} break;
		case RS::VIEWPORT_SDF_SCALE_25_PERCENT: {
			size[0] >>= 2;
			size[1] >>= 2;
			shift = 2;
			shrink = true;
		} break;
		default: {
		};
	}
	GLuint temp_fb;
	glGenFramebuffers(1, &temp_fb);