fix(filesystem): follow_current_file logic error

[julianbuettner]

Neotree did not follow_current_file in my neovim setup anymore, same thing happening to a colleague using Neotree.

I let a LLM investigate and apparently the bug is that "not" is stronger binding than comparison, so the line

not winpos == "current"
--equals
(not winpos) == "current"
-- equals
false == "current"

The suggested fix solved the problem for me.

[pynappo]

i'll merge b/c obviously the logic i wrote there was wrong, but for future reference can you write the reproduction steps needed to reproduce the issue? would be nice to have a test case to cover any future regressions