Remove discuss.python.org/c/packaging from issue choice selector

[pradyunsg]

Issue

Users are reaching out on the Packaging category for support regarding tox, who are not the right people to reach out to, by and large.

Example

https://discuss.python.org/t/tox-4-x-specify-multiline-lists-in-variables-or-expand-them-without-the-newline-characters/23654/

[jugmac00]

Thanks for the report. Will do after my break.

[jugmac00]

On a second thought... the intention is pretty clear "general ideas for Python packaging, questions about structuring projects and so on" and for that the link seems a good choice. Looks like people are not reading closely enough.

Maybe there is a better place for that link, e.g. in our documentation.