BOAPI-1096 fix(typecheck): delete {:ok, decimal} case

[zhabinka]

В elixir 1.19 TypeCheck стал более строгим.
У cast_decimal есть мёртвая ветка case:

==> tarams
Compiling 4 files (.ex)
    warning: the following clause will never match:

        {:ok, decimal}

    because it attempts to match on the result of:

        Decimal.parse(term)

    which has type:

        dynamic(
          :error or
            {%Decimal{sign: integer(), coef: integer(), exp: float() or integer()} or
               %Decimal{sign: integer(), coef: :NaN or :inf, exp: integer()}, term()}
        )

    typing violation found at:
    │
 66 │       {:ok, decimal} -> check_decimal(decimal, false)
    │       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    │
    └─ lib/type.ex:66: Tarams.Type.cast_decimal/1