Fix ut: remap default to classic similarity for indices created before 5.0.

core/src/main/java/org/elasticsearch/index/mapper/core/TypeParsers.java

@@ -445,7 +445,7 @@ public class TypeParsers {
     private static SimilarityProvider resolveSimilarity(Mapper.TypeParser.ParserContext parserContext, String name, String value) {
         if (parserContext.indexVersionCreated().before(Version.V_5_0_0_alpha1) && "default".equals(value)) {
             // "default" similarity has been renamed into "classic" in 3.x.
-            value = SimilarityService.DEFAULT_SIMILARITY;
+            value = "classic";
         }
         SimilarityProvider similarityProvider = parserContext.getSimilarity(value);
         if (similarityProvider == null) {