Rename the FIXMEs, remove a few that dont matter anymore

compiler/rustc_next_trait_solver/src/solve/effect_goals.rs

@@ -84,7 +84,7 @@ where
         let cx = ecx.cx();
         let mut candidates = vec![];
 
-        // FIXME(effects): We elaborate here because the implied const bounds
+        // FIXME(const_trait_impl): We elaborate here because the implied const bounds
         // aren't necessarily elaborated. We probably should prefix this query
         // with `explicit_`...
         for clause in elaborate::elaborate(

compiler/rustc_next_trait_solver/src/solve/trait_goals.rs

@@ -609,8 +609,6 @@ where
             return Err(NoSolution);
         }
 
-        // FIXME(effects): Implement this when we get const working in the new solver
-
         // `Destruct` is automatically implemented for every type in
         // non-const environments.
         ecx.probe_builtin_trait_candidate(BuiltinImplSource::Misc)