Version for spyder 6

[rellieberman]

After upgrading to spyder 6, the terminal is no longer accessible.
It looks as if the new version of spyder is not compatible with spyder-terminal.

[Zybulon]

Hello,

The issue has already been reported here #345.
I have a pull request #349 that corrects it.
However the tests do not pass yet. They failed not because of the corrections I made but because of the dependencies are too old.
Honestly I don't think I would have time to make the tests pass. So I think I'll stop here, unless someone update the tests.