docs(contributing): fix outdated issue tracker links

[AkaHarshit]

Summary of the problem

The CONTRIBUTING.md guide still references the legacy learnboost/mongoose GitHub repository in the "Requesting new features" and "Fixing bugs / Adding features" sections. These outdated links can send contributors to the wrong issue tracker, making it harder to report bugs or request features in the active Automattic/mongoose repository.

Explanation of the solution

• Updated all remaining https://github.com/learnboost/mongoose/... links in CONTRIBUTING.md to point to https://github.com/Automattic/mongoose/....
• Kept the existing wording and structure of the contribution guide intact, only changing the repository owner in the URLs.
• Ensured the bug-reporting section, feature-request section, and fixing-bugs section now consistently reference the same, current issue tracker.

Before vs After behavior

• Before

  • "Requesting new features" linked to https://github.com/learnboost/mongoose/issues and https://github.com/learnboost/mongoose/issues/new.
  • "Fixing bugs / Adding features" linked to the same learnboost/mongoose issue URLs.
  • Contributors could be redirected to an outdated repository when filing or browsing issues.

• After

  • All issue tracker links in CONTRIBUTING.md now consistently use https://github.com/Automattic/mongoose/issues and https://github.com/Automattic/mongoose/issues/new.
  • New contributors are guided to the active Automattic/mongoose issue tracker when reporting bugs or requesting features.

Testing performed

• Documentation-only change; no runtime code affected.
• Manually verified that all updated URLs resolve to the correct pages in the Automattic/mongoose repository and that there are no remaining learnboost/mongoose issue links in CONTRIBUTING.md.

[AbdelrahmanHafez]

Thanks!

[vkarpov15]

Thanks 👍