Remove wrong _comp_priv_prefix

[Freed-Wu]

See https://github.com/inducer/pudb/pull/554#issuecomment-1250708829 and https://github.com/inducer/pudb/pull/554#issuecomment-1250716904, the wrong _comp_priv_prefix must be removed.

[rofl0r]

when i merged the zsh completion i assumed this is a one-off favor, but this is now the 3rd edit. i don't want to clutter the git commit history with zsh completion changes and spend more time with it, so you get one last chance to get this right, else i will remove it again. so take your time to make this the ultimate and final fix.

[Freed-Wu]

OK, wait for enough long time to ensure nothing wrong happen. (BTW, even if this change isn't merged, it will not affect anyone. This change does not fix a bug, just remove some unused code, so we can have enough time.)

And this script is not generated automatically (go/rust/python have libraries to generate shell completion script automatically), so if new option is added or old option has changed, the script should be changed manually, which is troublesome. It is the biggest weakness. Maybe something like https://github.com/mirror/x264/blob/master/autocomplete.c is a better method.

[rofl0r]

is this good to merge now ?

[Freed-Wu]

• I change the file path to completions/zsh/_proxychains, which should be less confused.
• Now it should be the final work.

[Freed-Wu]

@rofl0r