Remove agnostic term from the `octez-agnostic-baker`

Once the protocol-specific baking binaries are deprecated officially (and the #7763 issue is closed), we should rename the octez-agnostic-baker to its final intended name, which is octez-baker, as the only baker binary that the users should use. Or this can be done in parallel, as one does not block the other, but they should both belong in the same version release.

This work should be similar to !17491 (merged)