fix: remove unused type parameters.

[youngsofun]

receive warning from cargo clippy.

Which issue does this PR close?

Closes #.

Rationale for this change

cargo clippy --future-incompat-report


warning: type parameter goes unused in function definition
  --> arrow-ord/src/ord.rs:48:18
   |
48 | fn compare_string<T>(left: &dyn Array, right: &dyn Array) -> DynComparator
   |                  ^^^
   |
   = help: consider removing the parameter
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#extra_unused_type_parameters
   = note: `#[warn(clippy::extra_unused_type_parameters)]` on by default

warning: type parameter goes unused in function definition
   --> arrow-ord/src/sort.rs:904:17
    |
904 | fn sort_list<S, T>(
    |                 ^
    |
    = help: consider removing the parameter
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#extra_unused_type_parameters

What changes are included in this PR?

Are there any user-facing changes?