Replaced Obsolete attributes in WhenCalled<T> with doc comments.

Author: Mihnea Rădulescu

src/NSubstitute/Core/WhenCalled.cs

@@ -7,9 +7,6 @@ namespace NSubstitute.Core;
 
 public class WhenCalled<T>(ISubstitutionContext context, T substitute, Action<T> call, MatchArgs matchArgs)
 {
-    private const string RecommendedThrowMethodToUseMessage =
-        "The recommended method to use is Throw().";
-
     private readonly ICallRouter _callRouter = context.GetCallRouterFor(substitute!);
     private readonly IThreadLocalContext _threadContext = context.ThreadContext;
     private readonly IRouteFactory _routeFactory = context.RouteFactory;
@@ -77,21 +74,21 @@ public void Throw(Func<CallInfo, Exception> createException) =>
     /// <summary>
     /// Throws the specified exception when called.
     /// </summary>
-    [Obsolete(RecommendedThrowMethodToUseMessage)]
+    /// Prefer <see cref="Throw(System.Exception)" /> for readability.
     public void Throws(Exception exception) =>
         Throw(exception);
 
     /// <summary>
     /// Throws an exception of the given type when called.
     /// </summary>
-    [Obsolete(RecommendedThrowMethodToUseMessage)]
+    /// Prefer <see cref="Throw{TException}" /> for readability.
     public TException Throws<TException>() where TException : Exception, new()
         => Throw<TException>();
 
     /// <summary>
     /// Throws an exception generated by the specified function when called.
     /// </summary>
-    [Obsolete(RecommendedThrowMethodToUseMessage)]
+    /// Prefer <see cref="Throw(System.Func{CallInfo, System.Exception})" /> for readability.
     public void Throws(Func<CallInfo, Exception> createException) =>
         Throw(createException);
 }