update comment

compiler/rustc_middle/src/traits/mod.rs

@@ -292,8 +292,7 @@ pub enum ObligationCauseCode<'tcx> {
         trait_item_def_id: DefId,
     },
 
-    /// Checking that this expression can be assigned where it needs to be
-    // FIXME(eddyb) #11161 is the original Expr required?
+    /// Checking that this expression can be assigned to its target.
     ExprAssignable,
 
     /// Computing common supertype in the arms of a match expression