housekeeping: Use newer Github Actions setup

[worldbeater]

What kind of change does this PR introduce?

This PR incorporates the changes from reactiveui/ReactiveUI.Validation#156

Apparently, there is no issues with codecov in this repository, but probably worth using the same yml template anyway?

[codecov]

Codecov Report

Merging #620 into main will increase coverage by 1.97%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #620      +/-   ##
==========================================
+ Coverage   68.49%   70.47%   +1.97%     
==========================================
  Files          75       75              
  Lines        4003     4003              
  Branches      386        0     -386     
==========================================
+ Hits         2742     2821      +79     
- Misses       1179     1182       +3     
+ Partials       82        0      -82     

Impacted Files	Coverage Δ
...ceMonitoring/DefaultFeatureUsageTrackingSession.cs
a/splat/splat/src/Splat/Logging/DebugLogger.cs
.../splat/splat/src/Splat/Logging/LoggingException.cs
...splat/splat/src/Splat/Maths/PointMathExtensions.cs
...t.Microsoft.Extensions.Logging/MsLoggingHelpers.cs
...t/splat/src/Splat/Disposables/BooleanDisposable.cs
...splat/src/Splat.AppCenter/AppCenterViewTracking.cs
a/splat/splat/src/Splat/Logging/LogHost.cs
...splat/splat/src/Splat.Drawing/Colors/SplatColor.cs
...plat/splat/src/Splat/Logging/WrappingFullLogger.cs
... and 140 more

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[github-actions]

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