chore(docs): fix setup steps in contributing doc

[dreamorosi]

Description of your changes

The PR updates the contributing docs by clarifying that prospective contributors should be using [email protected] instead of 8.x like previously stated.

The change is needed because the 9.x version comes bundled with the Node.js version used by the project.

Additionally, as housekeeping item, the PR also removes a redundant { target="_blank" } notation in a link that was present in all README files.

Once merged, this PR closes #1477.

Related issues, RFCs

Issue number: #1477

Checklist

• My changes meet the tenets criteria
• I have performed a self-review of my own code
• I have commented my code where necessary, particularly in areas that should be flagged with a TODO, or hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my change is effective and works
• The PR title follows the conventional commit semantics

Breaking change checklist

Is it a breaking change?: NO

• I have documented the migration process
• I have added, implemented necessary warnings (if it can live side by side)

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