fix TestInt7HnswBackwardsCompatibility (#14460)

Author: gf2121

lucene/backward-codecs/src/test/org/apache/lucene/backward_index/TestInt7HnswBackwardsCompatibility.java

@@ -21,7 +21,9 @@
 import com.carrotsearch.randomizedtesting.annotations.ParametersFactory;
 import java.io.IOException;
 import org.apache.lucene.codecs.Codec;
+import org.apache.lucene.codecs.KnnVectorsFormat;
 import org.apache.lucene.codecs.KnnVectorsReader;
+import org.apache.lucene.codecs.lucene101.Lucene101Codec;
 import org.apache.lucene.codecs.lucene99.Lucene99HnswScalarQuantizedVectorsFormat;
 import org.apache.lucene.codecs.lucene99.Lucene99HnswVectorsFormat;
 import org.apache.lucene.codecs.lucene99.Lucene99HnswVectorsReader;
@@ -67,10 +69,14 @@ public static Iterable<Object[]> testVersionsFactory() throws IllegalAccessExcep
   }
 
   protected Codec getCodec() {
-    return TestUtil.alwaysKnnVectorsFormat(
-        new Lucene99HnswScalarQuantizedVectorsFormat(
+    return new Lucene101Codec() {
+      @Override
+      public KnnVectorsFormat getKnnVectorsFormatForField(String field) {
+        return new Lucene99HnswScalarQuantizedVectorsFormat(
             Lucene99HnswVectorsFormat.DEFAULT_MAX_CONN,
-            Lucene99HnswVectorsFormat.DEFAULT_BEAM_WIDTH));
+            Lucene99HnswVectorsFormat.DEFAULT_BEAM_WIDTH);
+      }
+    };
   }
 
   @Override