classification enhancement (langchain4j#2052)

## Issue

when the EmbeddingModelTextClassifier has "higher" minScore, a lot of
useless LabelWithScore will be in the list labelsWithScores, and after
that will be filtered.

This is fix the check in the first for loop to not create useless
LabelWithScore and not to do more work on filter


## Change

## General checklist
- [x] There are no breaking changes
- [ ] I have added unit and integration tests for my change
- [x] I have manually run all the unit and integration tests in the
module I have added/changed, and they are all green
- [x] I have manually run all the unit and integration tests in the
[core](https://github.com/langchain4j/langchain4j/tree/main/langchain4j-core)
and
[main](https://github.com/langchain4j/langchain4j/tree/main/langchain4j)
modules, and they are all green
- [ ] I have added/updated the
[documentation](https://github.com/langchain4j/langchain4j/tree/main/docs/docs)
- [ ] I have added an example in the [examples
repo](https://github.com/langchain4j/langchain4j-examples) (only for
"big" features)
- [ ] I have added/updated [Spring Boot
starter(s)](https://github.com/langchain4j/langchain4j-spring) (if
applicable)

langchain4j/src/main/java/dev/langchain4j/classification/EmbeddingModelTextClassifier.java

@@ -128,11 +128,13 @@ public List<E> classify(String text) {
             }
             meanScore /= exampleEmbeddings.size();
 
-            labelsWithScores.add(new LabelWithScore(label, aggregatedScore(meanScore, maxScore)));
+            double aggregateScore = aggregatedScore(meanScore, maxScore);
+            if (aggregateScore >= minScore){
+                labelsWithScores.add(new LabelWithScore(label, aggregateScore));
+            }
         });
 
         return labelsWithScores.stream()
-                .filter(it -> it.score >= minScore)
                 // sorting in descending order to return highest score first
                 .sorted(comparingDouble(labelWithScore -> 1 - labelWithScore.score))
                 .limit(maxResults)