Improve setting description for default interpreter setting

[luabud]

Same issue as this: microsoft/vscode-mypy#144

Improve description of the default value of the setting. When it's set to [], it will use the Python extension's selected interpreter. If it's set to a path, it will use that value as the interpreter. See this PR: https://github.com/microsoft/vscode-mypy/pull/152/files

[luabud]

We are reserving this issue for Grace Hopper's Open Source Day, which will take place on September 22nd, 2023. If you're part of the event and would like to submit a contribution to this issue, please let us know, and we'll be happy to assign it to you.

For other community members who are not participating in the event, we appreciate your interest in contributing! We kindly request that you wait until after September 22nd to work on this issue. If no one from the event has been assigned to it by then, we'll gladly assign it to you. Thank you for your understanding and support!

[aku1310]

Hi @luabud, hope you're doing well!
I will be participating in GHC 2023 and I am interested to work on this issue. Do we have to wait until the Open Source Day starts to be assigned an issue or could it be assigned before as well?

[luabud]

@aku1310 done!