The world border can change in size when the game is paused

The Bug:

The world border can change in size when the game is paused.

Steps to Reproduce:

1. Enter a singleplayer world and set the world border to 10 blocks wide by using the command provided below.

   /worldborder set 10

2. Set the world border to 50 blocks wide over the course of 5 seconds by using the command provided below.

   /worldborder set 50 5

3. Pause the game and watch the world border.

Observed Behavior:

The world border can change in size when the game is paused.

Expected Behavior:

The world border would not be able to change in size when the game is paused.