Related to MC-219843. (parity issue)

The mycelium's side texture slightly differs from other dirt-based blocks such as grass blocks and podzol blocks.

How to Reproduce
1. Place down grass, podzol, and mycelium side by side.

Observed Result
The mycelium's side texture slightly differs from one another.

Expected Result
The mycelium's side texture is the same as one another, or as the Java fixes will provide.