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MINOR: [Dev] Add Bryce Mecum to list of collaborators (#38678)

### Rationale for this change

Disclaimer: is a colleague of mine.

Opening PR as documented on: https://arrow.apache.org/docs/developers/reviewing.html#collaborators 
Bryce Mecum (@ amoeba) has been helping with the project for some time and usually helps reviewing breaking changes and critical fixes in order to properly label the issues for the release.
It would be helpful if he can add the corresponding labels and assign issues.

### What changes are included in this PR?
Add to list of collaborators.

### Are these changes tested?

No

### Are there any user-facing changes?

No

Authored-by: Raúl Cumplido <raulcumplido@gmail.com>
Signed-off-by: Sutou Kouhei <kou@clear-code.com>