chore: Remove Zebra RFCs from CONTRIBUTING.md

[mpguerra]

We have deprecated the RFC process

Motivation

What are the most important goals of the ticket or PR?

PR Author Checklist

Check before marking the PR as ready for review:

• Will the PR name make sense to users?
• Does the PR have a priority label?
• Have you added or updated tests?
• Is the documentation up to date?

For significant changes:

• Is there a summary in the CHANGELOG?
• Can these changes be split into multiple PRs?

If a checkbox isn't relevant to the PR, mark it as done.

Specifications

Complex Code or Requirements

Solution

Testing

Review

Reviewer Checklist

Check before approving the PR:

• Does the PR scope match the ticket?
• Are there enough tests to make sure it works? Do the tests cover the PR motivation?
• Are all the PR blockers dealt with?
  PR blockers can be dealt with in new tickets or PRs.

And check the PR Author checklist is complete.

Follow Up Work

[oxarbitrage]

I understand the RFC process is deprecated but i think we might want to replace it with something as:

Large changes:

When adding a large change or a series of pull requests into Zebra please make sure the whole context is written in a ticket and link each piece is linking to it. Sometimes, it might be useful to request a meeting or discuss in chat channels with the Zebra team to agree in the process to be taken.

[mpguerra]

I understand the RFC process is deprecated but i think we might want to replace it with something as:

Large changes:

When adding a large change or a series of pull requests into Zebra please make sure the whole context is written in a ticket and link each piece is linking to it. Sometimes, it might be useful to request a meeting or discuss in chat channels with the Zebra team to agree in the process to be taken.

I think this can be done in a separate PR. Right now I think it's important that people don't spend time on a process that we no longer follow :)