chore(driver): Remove unused error variant NoValueToPropose, remove…

… `Env` trait

Code/driver/src/error.rs

@@ -7,9 +7,6 @@ pub enum Error<Ctx>
 where
     Ctx: Context,
 {
-    /// No value to propose
-    NoValueToPropose,
-
     /// Proposer not found
     ProposerNotFound(Ctx::Address),
 
@@ -27,7 +24,6 @@ where
     #[cfg_attr(coverage_nightly, coverage(off))]
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
-            Error::NoValueToPropose => write!(f, "No value to propose"),
             Error::ProposerNotFound(addr) => write!(f, "Proposer not found: {addr}"),
             Error::ValidatorNotFound(addr) => write!(f, "Validator not found: {addr}"),
             Error::InvalidVoteSignature(vote, validator) => write!(
@@ -46,7 +42,6 @@ where
     #[cfg_attr(coverage_nightly, coverage(off))]
     fn eq(&self, other: &Self) -> bool {
         match (self, other) {
-            (Error::NoValueToPropose, Error::NoValueToPropose) => true,
             (Error::ProposerNotFound(addr1), Error::ProposerNotFound(addr2)) => addr1 == addr2,
             (Error::ValidatorNotFound(addr1), Error::ValidatorNotFound(addr2)) => addr1 == addr2,
             (