staking(tests): check that the final definition upload is disabled

[cratelyn]

@cratelyn I don't know what the state of the art is for writing functional tests of staking component these days, but I figured I'd point you at this one so perhaps you can show me the way. Ideally this would be paired with a unit test preventing a regression that deletes this rule?

Originally posted by @plaidfinch in #4178 (comment)

https://github.com/penumbra-zone/penumbra/blob/main/crates/core/app/tests/app_can_define_and_delegate_to_a_validator.rs

app_can_define_and_delegate_to_a_validator.rs would be a good starting point, which defines and delegates to a validator.