fix unnecessary_to_owned about msrv

[kyoto7250]

This PR fixes [`unnecessary_owned`].

What

# sample code
fn _msrv_1_35() {
    #![clippy::msrv = "1.35"]
    let _ = &["x"][..].to_vec().into_iter();
}

fn _msrv_1_36() {
    #![clippy::msrv = "1.36"]
    let _ = &["x"][..].to_vec().into_iter();
}

If we will check this code using clippy, [`unnecessary_owned`] will modify the code as follows.

error: unnecessary use of `to_vec`
  --> $DIR/unnecessary_to_owned.rs:219:14
   |
LL |     let _ = &["x"][..].to_vec().into_iter();
   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use: `["x"][..].iter().copied()`

error: unnecessary use of `to_vec`
  --> $DIR/unnecessary_to_owned.rs:224:14
   |
LL |     let _ = &["x"][..].to_vec().into_iter();
   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use: `["x"][..].iter().copied()`

This is incorrect. Because Iterator::copied was estabilished in 1.36.

Why

This bug was caused by not separating "copied" and "clone" by reference to msrv.

rust-clippy/clippy_lints/src/methods/unnecessary_to_owned.rs

Line 195 in 89ee6aa

let cloned_or_copied = if is_copy(cx, item_ty) { "copied" } else { "cloned" };

So, I added a conditional branch and described the corresponding test.

Thank you in advance.

changelog: fix wrong suggestions about msrv in [unnecessary_to_owned]

r! @giraffate

[rust-highfive]

r? @giraffate

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[giraffate]

@bors r+

It looks good, thanks!

[bors]

📌 Commit dfdc5ad has been approved by giraffate

[bors]

⌛ Testing commit dfdc5ad with merge f70c73f...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: giraffate
Pushing f70c73f to master...