Calling `load_module` twice each with different packages removes the first one

[nabenabe0928]

Execute the following twice with optunahub==0.3.1:

import optunahub


optunahub.load_module("benchmarks/bbob")
optunahub.load_module("benchmarks/wfg")

Then we yield:

FileNotFoundError: [Errno 2] No such file or directory: '/home/shuhei/.cache/optunahub/github.com/optuna/optunahub-registry/main/package/benchmarks/bbob/__init__.py'

Environment

• Python 3.12
• Ubuntu 22.04
• OptunaHub 0.3.1

[nabenabe0928]

It may be fixed in the main head.