Update `Code of conduct for modding and mapping`

[MChecaH]

First change of the suite of changes prepared to improve the Wiki's current modding resources.

This one is focused on simplifying, rewording, and improving the current Modding Code of Conduct article. The contents deleted will be moved to their respective articles, decluttering the CoC in turn.

The project is being tracked in the following Issue and the following osu! Discord server thread.

Note for later; The broken wiki links in Common modding mistakes, Forum modding, and Modding will need to be changed by the new articles, once those are ready.

Self-check

• [x] The changes are tested against the contribution checklist
• [ ] The changes are reviewed by the team working on the rework.
• [ ] The changes are reviewed by the team who will enforce them (Mainly NAT and map/mod GMTs).