bitcoin-wallet: Add a missing closing parenthesis in the help
bitcoin-wallet: Add a missing closing parenthesis in the help

Summary: Backport of Core [[https://github.com/bitcoin/bitcoin/pull/16863 | PR16863]]

Test Plan: `ninja && src/bitcoin-wallet -help`

Reviewers: O1 Bitcoin ABC, #bitcoin_abc, jasonbcox

Reviewed By: O1 Bitcoin ABC, #bitcoin_abc, jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D7957

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