Conform to RDAP Response Profile 15feb19

This is only about the Response Profile, not the Technical Implementation guide.

The Response Profile can be found at https://www.icann.org/en/system/files/files/rdap-response-profile-15feb19-en.pdf

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=250277559

javatests/google/registry/rdap/RdapDataStructuresTest.java

@@ -45,7 +45,7 @@ public final class RdapDataStructuresTest {
   @Test
   public void testRdapConformance() {
     assertThat(RdapConformance.INSTANCE.toJson())
-        .isEqualTo(createJson("['icann_rdap_response_profile_0']"));
+        .isEqualTo(createJson("['rdap_level_0','icann_rdap_response_profile_0']"));
   }
 
   @Test