Chorus plants can spread outside of the world border

The Bug:

Chorus plants can spread outside of the world border.

Steps to Reproduce:

1. Place down several chorus flowers along the edge of the world border.
2. Set the "randomTickSpeed" gamerule to a high value in order to speed up the process of the chorus flowers growing by using the command provided below.

   /gamerule randomTickSpeed 1000

3. Watch the chorus plants closely as they spread.
4. Take note as to whether or not chorus plants can spread outside of the world border.

Observed Behavior:

Chorus plants can spread outside of the world border.

Expected Behavior:

Chorus plants would not be able to spread outside of the world border.