They get deprecated real fast, and since you can target a specific SDK
version the runner used shouldn't matter that much. Hopefully.

This avoids a future incompatibility issue.

robbert-vdh#202
rust-lang/rust#127323

20.04 is no longer supported by GitHub Actions.

Nothing sparks more joy than things that worked previously suddenly
refusing to work because it's more than a year old.

`16c6c58f4d9f08c9c515c991c218bff235cff6e2` changed this to no longer
refer to a specific runner (which should be fine with the target SDK
option), but there was a typo in there.

robbert-vdh#201

Love these deprecations.

20.04 is probably going to be removed soon.

Because the V3 versions no longer work.

Apparently the `macos-latest` runner silently changed architectures with
the macOS 14 update. Fun.

This was triggering a new deny-by-default lint in recent nightly
versions.

Resolved warning: use of deprecated function std::arch::x86_64::_MM_GET_FLUSH_ZERO_MODE

Issue robbert-vdh#220
Issue Link: robbert-vdh#220

Before:
   Compiling nih_plug v0.0.0
warning: hiding a lifetime that's elided elsewhere is confusing
   --> src\params\smoothing.rs:248:17
    |
248 |     pub fn iter(&self) -> SmootherIter<T> {
    |                 ^^^^^     --------------- the same lifetime is hidden here
    |                 |
    |                 the lifetime is elided here
    |
    = help: the same lifetime is referred to in inconsistent ways, making the signature confusing
    = note: `#[warn(mismatched_lifetime_syntaxes)]` on by default
help: use `'_` for type paths
    |
248 |     pub fn iter(&self) -> SmootherIter<'_, T> {
    |                                        +++

warning: `nih_plug` (lib) generated 1 warning
    Finished `release` profile [optimized] target(s) in 2.27s

After:
   Compiling nih_plug v0.0.0
    Finished `release` profile [optimized] target(s) in 2.27s