Simplify logic for RescoreKnnVectorQuery now that k is not modifiable

Author: carlosdelest

server/src/main/java/org/elasticsearch/index/mapper/vectors/DenseVectorFieldMapper.java

@@ -2137,7 +2137,6 @@ && isNotUnitVector(squaredMagnitude)) {
                     name(),
                     queryVector,
                     similarity.vectorSimilarityFunction(indexVersionCreated, ElementType.FLOAT),
-                    k,
                     knnQuery
                 );
             }

server/src/test/java/org/elasticsearch/search/vectors/RescoreKnnVectorQueryTests.java

@@ -77,7 +77,6 @@ public void testRescoreDocs() throws Exception {
                     FIELD_NAME,
                     queryVector,
                     VectorSimilarityFunction.COSINE,
-                    adjustedK,
                     new MatchAllDocsQuery()
                 );
 
@@ -143,7 +142,6 @@ private void checkProfiling(float[] queryVector, IndexReader reader, Query inner
             FIELD_NAME,
             queryVector,
             VectorSimilarityFunction.COSINE,
-            k,
             innerQuery
         );
         IndexSearcher searcher = newSearcher(reader, true, false);