fix example ssv-keys versions · ssvlabs/ssv-keys@9186e24

The following actions uses node12 which is deprecated and will be forced to run on node16: actions/checkout@v2, actions/setup-node@v1. For more info: https://github.blog/changelog/2023-06-13-github-actions-all-actions-will-run-on-node16-instead-of-node12-by-default/

'IsOptional' is defined but never used

'ValidateNested' is defined but never used

'IsString' is defined but never used

'Length' is defined but never used

'ValidateNested' is defined but never used

'IsOptional' is defined but never used

'IsNumber' is defined but never used

'OpeatorsListValidator' is defined but never used

'PublicKeyValidator' is defined but never used

'OwnerAddressValidator' is defined but never used

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