kernel: util: static ref deref return type

[bradjc]

Pull Request Overview

I updated the Rust compiler to a February 2023 nightly, and encountered build errors. Specifically:

error: impl method assumes more implied bounds than the corresponding trait method
  --> kernel/src/utilities/static_ref.rs:40:24
   |
40 |     fn deref(&self) -> &'static T {
   |                        ^^^^^^^^^^ help: replace this type to make the impl signature compatible: `&T`
   |
   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
   = note: for more information, see issue #105572 <https://github.com/rust-lang/rust/issues/105572>

Again, this changes a very core file, which I don't think should be swept up in an "Update Nightly" pr.

Testing Strategy

This pull request was tested by travis.

TODO or Help Wanted

n/a

Documentation Updated

• Updated the relevant files in /docs, or no updates are required.

Formatting

• Ran make prepush.

[hudson-ayers]

bors r+

[bors]

Build succeeded:

• ci-build (macos-latest)
• ci-build (ubuntu-latest)
• ci-format (ubuntu-latest)
• ci-qemu
• ci-tests (macos-latest)
• ci-tests (ubuntu-latest)