Maximum value for `MultiplierUpdate` (#12282)

* Maximum value for MultiplierUpdate

* Update frame/transaction-payment/src/lib.rs

Co-authored-by: Stephen Shelton <[email protected]>

* Update lib.rs

* return constant

* fix in runtime

* Update frame/transaction-payment/src/lib.rs

Co-authored-by: Kian Paimani <[email protected]>

* Update frame/transaction-payment/src/lib.rs

Co-authored-by: Kian Paimani <[email protected]>

* fixes

* remove unused import

* Update lib.rs

* more readable

* fix

* fix nits

Co-authored-by: Stephen Shelton <[email protected]>
Co-authored-by: Kian Paimani <[email protected]>