Change BWC versions on create index response

This commit changes the BWC versions on the create index response now
that the index name in the response is supported since 5.6.0.

Relates #25139

core/src/main/java/org/elasticsearch/action/admin/indices/create/CreateIndexResponse.java

@@ -50,7 +50,7 @@ public class CreateIndexResponse extends AcknowledgedResponse {
         super.readFrom(in);
         readAcknowledged(in);
         shardsAcked = in.readBoolean();
-        if (in.getVersion().onOrAfter(Version.V_6_0_0_alpha3)) {
+        if (in.getVersion().onOrAfter(Version.V_5_6_0)) {
             index = in.readString();
         }
     }
@@ -60,7 +60,7 @@ public class CreateIndexResponse extends AcknowledgedResponse {
         super.writeTo(out);
         writeAcknowledged(out);
         out.writeBoolean(shardsAcked);
-        if (out.getVersion().onOrAfter(Version.V_6_0_0_alpha3)) {
+        if (out.getVersion().onOrAfter(Version.V_5_6_0)) {
             out.writeString(index);
         }
     }

rest-api-spec/src/main/resources/rest-api-spec/test/indices.create/10_basic.yml

@@ -33,7 +33,7 @@
 ---
 "Create index":
   - skip:
-      version: " - 5.99.99"
+      version: " - 5.5.99"
       reason: create index response contains index name since 5.6.0
 
   - do: