Increase output token limit for EquivalenceEvaluator (#6835)

EquivalenceEvaluator was specifying MaxOutputTokens = 1 since its prompt instructs the LLM to produce a response (score) that is a single digit (between 1 and 5).

Turns out that while this works for most models (including the OpenAI models that were used to test the prompt), some models require more than one token for this. For example, looks like Claude requires two tokens for this - see #6814).

This PR bumps the MaxOutputTokens to 5 to address the above issue.

Fixes #6814

Author: shyamnamboodiripad

src/Libraries/Microsoft.Extensions.AI.Evaluation.Quality/EquivalenceEvaluator.cs

@@ -52,7 +52,7 @@ public sealed class EquivalenceEvaluator : IEvaluator
         new ChatOptions
         {
             Temperature = 0.0f,
-            MaxOutputTokens = 1,
+            MaxOutputTokens = 5, // See https://github.com/dotnet/extensions/issues/6814.
             TopP = 1.0f,
             PresencePenalty = 0.0f,
             FrequencyPenalty = 0.0f,