Update OWNERS on operator 🙃
Update OWNERS on operator 🙃

This changes does 3 things:
- Removes @sthaha from approvers (as inactive for a long time 🙏)
- Move @sm43 to approvers
- Adds @concaf to reviewers

Signed-off-by: Vincent Demeester <b98c0fd48a8945096c766de790fe70420dd2f223@redhat.com>

tektoncd/operator,tektoncd/operator,tektoncd/operator