Entity shadows appear on signs when stacked

Shadows that appear from signs now render on signs when placed in a vertical manner. In 1.16.40, this does not occur.

Steps to Reproduce

1. Place a sign

2. Place another sign on top of the one previously placed

Here, the shadow will render, which doesn't happen in 1.16.40.

Video Example

https://youtu.be/kFSgcdHZs2Q