Revert "Auto merge of #91354 - fee1-dead:const_env, r=spastorino"

This reverts commit 18bb8c61a9, reversing
changes made to d9baa36190.

compiler/rustc_infer/src/traits/mod.rs

@@ -69,16 +69,6 @@ impl PredicateObligation<'tcx> {
     }
 }
 
-impl TraitObligation<'tcx> {
-    /// Returns `true` if the trait predicate is considered `const` in its ParamEnv.
-    pub fn is_const(&self) -> bool {
-        match (self.predicate.skip_binder().constness, self.param_env.constness()) {
-            (ty::BoundConstness::ConstIfConst, hir::Constness::Const) => true,
-            _ => false,
-        }
-    }
-}
-
 // `PredicateObligation` is used a lot. Make sure it doesn't unintentionally get bigger.
 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
 static_assert_size!(PredicateObligation<'_>, 32);