Remove "Known problems" section for borrow_interior_mutable_const (rust-lang#14078)

Remove "Known problems" section for `borrow_interior_mutable_const`
since issue were fixed some time ago - rust-lang#6110, rust-lang#5812

changelog: none

Author: Manishearth

clippy_lints/src/non_copy_const.rs

@@ -89,16 +89,6 @@ declare_clippy_lint! {
     ///
     /// The `const` value should be stored inside a `static` item.
     ///
-    /// ### Known problems
-    /// When an enum has variants with interior mutability, use of its non
-    /// interior mutable variants can generate false positives. See issue
-    /// [#3962](https://github.com/rust-lang/rust-clippy/issues/3962)
-    ///
-    /// Types that have underlying or potential interior mutability trigger the lint whether
-    /// the interior mutable field is used or not. See issues
-    /// [#5812](https://github.com/rust-lang/rust-clippy/issues/5812) and
-    /// [#3825](https://github.com/rust-lang/rust-clippy/issues/3825)
-    ///
     /// ### Example
     /// ```no_run
     /// use std::sync::atomic::{AtomicUsize, Ordering::SeqCst};