Rollup merge of #85689 - m-ou-se:array-intoiter-3, r=estebank

Remove Iterator #[rustc_on_unimplemented]s that no longer apply.

Now that `IntoIterator` is implemented for arrays, all the `rustc_on_unimplemented` for arrays of ranges (e.g. `for _ in [1..3] {}`) no longer apply, since they are now valid Rust.

Separated these from #85670, because we should discuss a potential new (clippy?) lint for these.

Until Rust 1.52, `for _ in [1..3] {}` produced:

```
error[E0277]: `[std::ops::Range<{integer}>; 1]` is not an iterator
 --> src/main.rs:2:14
  |
2 |     for _ in [1..3] {}
  |              ^^^^^^ if you meant to iterate between two values, remove the square brackets
  |
  = help: the trait `std::iter::Iterator` is not implemented for `[std::ops::Range<{integer}>; 1]`
  = note: `[start..end]` is an array of one `Range`; you might have meant to have a `Range` without the brackets: `start..end`
  = note: required by `std::iter::IntoIterator::into_iter`
```

But in Rust 1.53 and later, it compiles fine. It iterates over the array by value, for one iteration with the element `1..3`.

This is probably a mistake, which is no longer caught. Should we have a lint for it? Should Clippy have a lint for it?

cc ```@estebank``` ```@flip1995```

cc #84513

library/core/src/iter/traits/iterator.rs

@@ -25,40 +25,6 @@ fn _assert_is_object_safe(_: &dyn Iterator<Item = ()>) {}
 /// [impl]: crate::iter#implementing-iterator
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_on_unimplemented(
-    on(
-        _Self = "[std::ops::Range<Idx>; 1]",
-        label = "if you meant to iterate between two values, remove the square brackets",
-        note = "`[start..end]` is an array of one `Range`; you might have meant to have a `Range` \
-                without the brackets: `start..end`"
-    ),
-    on(
-        _Self = "[std::ops::RangeFrom<Idx>; 1]",
-        label = "if you meant to iterate from a value onwards, remove the square brackets",
-        note = "`[start..]` is an array of one `RangeFrom`; you might have meant to have a \
-              `RangeFrom` without the brackets: `start..`, keeping in mind that iterating over an \
-              unbounded iterator will run forever unless you `break` or `return` from within the \
-              loop"
-    ),
-    on(
-        _Self = "[std::ops::RangeTo<Idx>; 1]",
-        label = "if you meant to iterate until a value, remove the square brackets and add a \
-                 starting value",
-        note = "`[..end]` is an array of one `RangeTo`; you might have meant to have a bounded \
-                `Range` without the brackets: `0..end`"
-    ),
-    on(
-        _Self = "[std::ops::RangeInclusive<Idx>; 1]",
-        label = "if you meant to iterate between two values, remove the square brackets",
-        note = "`[start..=end]` is an array of one `RangeInclusive`; you might have meant to have a \
-              `RangeInclusive` without the brackets: `start..=end`"
-    ),
-    on(
-        _Self = "[std::ops::RangeToInclusive<Idx>; 1]",
-        label = "if you meant to iterate until a value (including it), remove the square brackets \
-                 and add a starting value",
-        note = "`[..=end]` is an array of one `RangeToInclusive`; you might have meant to have a \
-                bounded `RangeInclusive` without the brackets: `0..=end`"
-    ),
     on(
         _Self = "std::ops::RangeTo<Idx>",
         label = "if you meant to iterate until a value, add a starting value",