Remove runtime fields (#63418)

We are not going to release runtime fields with 7.10, hence we are removing them from the 7.10 branch.

Author: javanna

x-pack/plugin/ml/qa/native-multi-node-tests/src/javaRestTest/java/org/elasticsearch/xpack/ml/integration/DatafeedJobsRestIT.java

@@ -127,11 +127,6 @@ private void addAirlineData() throws IOException {
                 + "          \"keyword\":{\"type\":\"keyword\"}"
                 + "         }"
                 + "       },"
-                + "      \"airline_lowercase_rt\": { "
-                + "        \"type\":\"runtime\","
-                + "        \"runtime_type\": \"keyword\","
-                + "        \"script\" : { \"source\": \"emit(params._source.airline.toLowerCase())\" }"
-                + "      },"
                 + "      \"responsetime\": { \"type\":\"float\"}"
                 + "    }"
                 + "  }"
@@ -297,13 +292,6 @@ public void testLookbackOnlyWithScriptFields() throws Exception {
             .execute();
     }
 
-    public void testLookbackOnlyWithRuntimeFields() throws Exception {
-        new LookbackOnlyTestHelper("test-lookback-only-with-runtime-fields", "airline-data")
-            .setAirlineVariant("airline_lowercase_rt")
-            .setShouldSucceedProcessing(true)
-            .execute();
-    }
-
     public void testLookbackonlyWithNestedFields() throws Exception {
         String jobId = "test-lookback-only-with-nested-fields";
         Request createJobRequest = new Request("PUT", MachineLearning.BASE_PATH + "anomaly_detectors/" + jobId);