refactor(DssVestMintable): remove filtered clause from rule

Author: amusingaxl

certora/DssVestMintable.spec

@@ -59,7 +59,7 @@ invariant finGreaterOrEqualClf(uint256 _id) fin(_id) >= clf(_id);
 //     init_state axiom rxd(_id) == 0;
 // }
 
-rule rxdLessOrEqualTot(method f) filtered { f -> !f.isFallback } {
+rule rxdLessOrEqualTot(method f) {
     env e;
     uint256 _id;