fix: CI checkout auth + Wrmse test failure

- Publish.yml: Change workflow permissions from {} to contents:read
  to fix GITHUB_TOKEN having no scopes for actions/checkout@v4
- Wrmse.cs: Use DateTime.UtcNow instead of DateTime.MinValue in
  Update(double,double,double) to match Beta/Covariance pattern
- Bump version to 0.8.5

lib/VERSION

@@ -1 +1 @@
-0.8.4
+0.8.5

lib/errors/wrmse/Wrmse.cs

@@ -176,7 +176,8 @@ public sealed class Wrmse : AbstractBase
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public TValue Update(double actual, double predicted, double weight, bool isNew = true)
     {
-        return Update(new TValue(DateTime.MinValue, actual), new TValue(DateTime.MinValue, predicted), weight, isNew);
+        var now = DateTime.UtcNow;
+        return Update(new TValue(now, actual), new TValue(now, predicted), weight, isNew);
     }
 
     /// <summary>