Fix the mixed cluster REST test explain/11_basic_with_types.

qa/mixed-cluster/build.gradle

@@ -57,7 +57,6 @@ for (Version version : bwcVersions.wireCompatible) {
   tasks.getByName("${baseName}#mixedClusterTestRunner").configure {
     /* To support taking index snapshots, we have to set path.repo setting */
     systemProperty 'tests.path.repo', new File(buildDir, "cluster/shared/repo")
-    systemProperty 'tests.rest.blacklist', ['explain/11_basic_with_types/Explain body without query element'].join(',')
   }
 }
 

rest-api-spec/src/main/resources/rest-api-spec/test/explain/11_basic_with_types.yml

@@ -59,6 +59,7 @@ setup:
       catch: bad_request
       explain:
           index:  test_1
+          type:   test
           id:     id_1
           body:
             match_all: {}