simplify wording of root cert inclusion comment

[oclyke]

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Proposed Changes

This is a proposed change to README.md correcting wrong usage of "manor" instead of "manner" and removing redundant "also" which is already suggested by trailing "as well".

Checklist

• [x] Rebased/mergeable
• [x] Commit messages are conventional
• [x] Sign CLA (if not already signed)

Note: tests and changelog not applicable