Clients can't sign proposals without `Sign` permission

[jshufro]

I have a vouch instance configured with [Sign beacon attestation, Sign beacon proposal, Access account] permissions, but it can't sign proposals and is failing with: ... "error":"failed to sign RANDAO reveal: failed to sign RANDAO reveal: failed to obtain signature: not enough signatures: 0 signed, 3 denied, 0 failed, 0 errored","message":"Failed to prepare beacon block proposal"}

This kind of implies a missing permission or missing documentation specifying that vouch needs Sign