Contributing.md still directs users to open bug reports

[bast0006]

Issue Description

vortex/CONTRIBUTING.md

Line 50 in d8f4461

[GitHub issue](https://github.com/vortex-data/vortex/issues).

Expected Behavior

Contributing.md should direct users to open a discussion, as per #5495

Actual Behavior

Users are directed to file a new issue

Reproduction Steps

Navigate to contributing.md

OS Version Information

N/A

I acknowledge that:

• I have searched the Vortex repository (both open and closed Discussions and Issues) and confirm this is not a duplicate of an existing issue or discussion.
• I have checked the "Preview" tab on all text fields to ensure that everything looks right, and have wrapped all configuration and code in code blocks with a group of three backticks (```) on separate lines.

[a10y]

Thanks for pointing this out @bast0006! I've opened #5657 to address this