Mangrove propagule has no random placement (in block)

Summary:
In the bedrock version of mangrove the propagule is always centered, while in the java version it is placed randomly in a block.

Steps to reproduce:

1. Place the mangrove propagule several times.
2. Look at the placement of the mangrove propagule in the block.

Observed results:
Mangrove propagule is always centered.

Expected results:
Will be randomly placed in the block (not centered).