Merging upstream CONTRIBUTING.md directly may lead to misunderstandings

[gongfuture]

I tried to submit a PR after completing the translation update, and at this point, GitHub reminded me that CONTRIBUTING.md had been updated two weeks ago. I opened it to check and found it was an update regarding the Localization section. Following the instructions, I registered on Weblate and attempted to translate at https://hosted.weblate.org/engage/ddnet/. Subsequently, I discovered that this is the translation link for ddnet official upstream, but it was also merged into this project in the commit at e5f5bbe.

I think this part needs to be modified.

[SollyBunny]

The section should be commented out instead of removed to reduce conflicts, the old description can then be added back