[BUG] AssertionError: MiniGrid-Empty-5x5-v0 is not supported

[Howuhh]

Describe the bug

Can not create MiniGrid environments.

To Reproduce

import envpool
envpool.make("MiniGrid-Empty-5x5-v0", env_type="gym")

System info

import envpool, numpy, sys
print(envpool.__version__, numpy.__version__, sys.version, sys.platform)

0.8.3 1.25.2 3.10.11 (main, Apr 20 2023, 19:02:41) [GCC 11.2.0] linux

Checklist

• [x] I have checked that there is no similar issue in the repo (required)
• [x] I have read the documentation (required)
• [x] I have provided a minimal working example to reproduce the bug (required)