Follow-up from "doc: Rename to Octez - Sweep 2"

The following discussion from !6784 (merged) should be addressed:

@sol.lederer started a discussion: (+5 comments)
In some instances where we say Tezos, it's ambiguous to me if it should be Octez. Places where we're talking about the codebase, which is still tezos, but we then refer to the code or project which should be octez.

E.g. within:
```
/docs/developer/contributing.rst
/docs/developer/guidelines.rst
/docs/developer/repository_scope.rst
/docs/introduction/howtouse.rst
```