Update README to not require safeUnwrap after 8.0.0

[chribjel]

After this release, the docs became slightly outdated.

This PR adds notices that it only applies for version 8.0.0 and earlier

[changeset-bot]

⚠️ No Changeset found

Latest commit: 4a27acf

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[supermacro]

Hey! Thank you for the contribution, but this PR has been merged instead: #600

[chribjel]

Understandable!