doc: Rename Tezos to Octez in the text

Context

This is to address #4377.

Previous MRs renamed references of tezos binaries to octez. However most of the textual descriptions still uses Tezos where Octez should be used. This MR is to rename them to Octez throughout the documentation where appropriate.

Manually testing the MR

Read to ensure there aren't instances that were renamed to Octez but should actually remain Tezos. Some situations are a bit subtle.

Checklist

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