Remove obsolete FAIR badge, update badge names

[Zeitsperre]

Pull Request Checklist:

• This PR addresses an already opened issue (for bug fixes / features)
  • This PR fixes [OpenSSF] Complete OpenSSF Best Practices recommendations #1181
• Tests for the changes have been added (for bug fixes / features)
  • (If applicable) Documentation has been added / updated (for bug fixes / features)
• CHANGELOG.rst has been updated (with summary of main changes)
  • Link to issue (:issue:number) and pull request (:pull:number) has been added

What kind of change does this PR introduce?

• Removes the FAIR Software badge (requirements already covered in OSSF Best Practices badge)

Does this PR introduce a breaking change?

No.

Other information:

The OSSF Scorecard should update to passing in the next day. xclim satisfies ~70% of the requirements for OSSF silver. More analysis is needed to evaluate whether this level is feasible for us.