Proto: rename constant to testnet_dictator
Related to !4547 (merged) which was just merged.
There was a bit of back and forth on how should the constant be named.
See discussion: !4547 (comment 855231173)
But after further consultations, it is evident that such a name is prone to misinterpretation in the context of the Tezos mainnet.
We are renaming it to testnet_dictator
to unambiguously state in the
code that this mechanism only works on testnets. We will be editing the
tzip as well to the same effect.
Edited by Mehdi Bouaziz