Fix: #AR-7659 minor link update for eth_sign

[shaloo]

PR

Describe your changes

eth_signTransaction is not supported and eth_sign is - fix its link in the usage guide.

Issue ticket number and link

• AR-7659

Checklist before requesting a review

• You have performed a self-review of your own code
• You are using approved terminology
• Your changes have been tested locally
• Your code builds clean without any errors or warnings

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