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
RBMap<uint32_t, RenderTarget::RTOverridden::FBOCacheEntry>::Element *cache;
	if ((cache = rt->overridden.fbo_cache.find(hash_key)) != nullptr) {
		rt->fbo = cache->get().fbo;
		rt->color = cache->get().color;
		rt->depth = cache->get().depth;
		rt->size = cache->get().size;
		rt->texture = p_color_texture;
		return;
	}
	_update_render_target(rt);
	RenderTarget::RTOverridden::FBOCacheEntry new_entry;
	new_entry.fbo = rt->fbo;
	new_entry.color = rt->color;
	new_entry.depth = rt->depth;
	new_entry.size = rt->size;
	
	if (p_color_texture.is_null()) {
		new_entry.allocated_textures.push_back(rt->color);
	}
	if (p_depth_texture.is_null()) {
		new_entry.allocated_textures.push_back(rt->depth);
	}
	rt->overridden.fbo_cache.insert(hash_key, new_entry);
}
RID TextureStorage::render_target_get_override_color(RID p_render_target) const {
	RenderTarget *rt = render_target_owner.get_or_null(p_render_target);
	ERR_FAIL_COND_V(!rt, RID());
	return rt->overridden.color;
}
RID TextureStorage::render_target_get_override_depth(RID p_render_target) const {