fix: keyring-backend flag usage

[robert-zaremba]

Description

./build/simd keys --help shows wrong --keyring-backend usage doc:

--keyring-backend string   Select keyring's backend (os|file|test) (default "os")

It's missing pass and memory.

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[sonarcloud]

[Cosmos SDK] Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
1 Code Smell

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[julienrbrt]

lgtm, can you gofumpt?