Added admin_secret_ky circuit stub

[Yiakman]

This should fix the

[MidnightActions] Failed to initialize action contract:
CompactError: first (witnesses) argument to Contract constructor
does not contain a function-valued field named admin_secret_key
    at new Contract (.../go-fish-contract/src/game.compact:157:1)
    at initializeActionContract (.../midnight-actions.ts:355:22)
    at file:///mnt/data/go-fish/packages/client/node/src/main.mainnet.ts:67:5

error in the logs