Bump Elasticsearch codec to track Lucene101Codec

Author: ChrisHegarty

server/src/test/java/org/elasticsearch/index/mapper/CompletionFieldMapperTests.java

@@ -162,7 +162,7 @@ public void testPostingsFormat() throws IOException {
             assertThat(codec, instanceOf(LegacyPerFieldMapperCodec.class));
             assertThat(
                 ((LegacyPerFieldMapperCodec) codec).getPostingsFormatForField("field"),
-                instanceOf(Completion912PostingsFormat.class)
+                instanceOf(Completion101PostingsFormat.class)
             );
         }
     }