fix: Disable signMessage for near-wallet

[kujtimprenkuSQA]

Description

This PR stops/disables the ability to trigger signMessage for NEAR Wallet since it's not supported.

This will avoid redirecting to a 404 page in the cases when users sign-in with NEAR Wallet and try the signMessage, since near-wallet in our side just wraps around the my-near-wallet setup it was enabled by default.

Closes: #973

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings

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