bugfix for import local tools module failed

[jiaqianjing]

I think if you want to import local module (e.g. from toos import my_utils) by modifying sys.path, it's better to replace sys.path.apped() with sys.path.insert(). Because some tools has been exists in sys.path.

Traceback (most recent call last):
  File "/workspace/GPT-SoVITS/webui.py", line 44, in <module>
    from tools import my_utils
ImportError: cannot import name 'my_utils' from 'tools' (/opt/conda/lib/python3.10/site-packages/tools/__init__.py)

[jiaqianjing]

Otherwise you can set export PYTHONPATH=/path/to/GPT-SoVITS. This same as path/to/GPT-SoVITS insert to sys.path not append.