Update Octez binary and command names

Clarification and motivation

Since Octez version 15 Octez binaries have been renamed from tezos-* to octez-*.

Currently aliases are still available for previous names, but they are supposed to disappear as time goes on.

We should adapt this tutorial as well to used the new names when mentioning binaries and commands that have been renamed.

Acceptance criteria

The commands and binaries in the tutorial use to the new octez-* names rather than the old tezos-* ones.