Clearer Nether Wart Growth

Changes Nether Wart to have distinct textures for each growth stage and a more full final stage texture (just like pre-1.14). This texture was created by JAPPA and included in developmental versions of the Texture Update, but it did not make the full release for some reason.

I personally find it difficult to tell if Nether Wart is fully grown in Vanilla, and this pack makes it much easier.