[Security Solution][Endpoint] Remove responder FTR test (elastic#175454)

## Summary

Delete responder test skipped in elastic/pull/170489.
We've cypress tests that cover the test cases here.

### Flaky runner
-
https://buildkite.com/elastic/kibana-flaky-test-suite-runner/builds/4937
x 50 (...)

### Checklist

- [x] [Flaky Test
Runner](https://ci-stats.kibana.dev/trigger_flaky_test_runner/1) was
used on any tests changed

x-pack/test/security_solution_endpoint/apps/endpoint/index.ts

@@ -45,7 +45,6 @@ export default function (providerContext: FtrProviderContext) {
     loadTestFile(require.resolve('./endpoint_list'));
     loadTestFile(require.resolve('./endpoint_telemetry'));
     loadTestFile(require.resolve('./endpoint_permissions'));
-    loadTestFile(require.resolve('./responder'));
     loadTestFile(require.resolve('./endpoint_solution_integrations'));
   });
 }

x-pack/test/security_solution_ftr/services/timeline/index.ts

@@ -58,6 +58,7 @@ export class TimelineTestService extends FtrService {
       await this.supertest
         .post(TIMELINE_DRAFT_URL)
         .set('kbn-xsrf', 'true')
+        .set('elastic-api-version', '2023-10-31')
         .send({ timelineType: 'default' })
         .then(this.getHttpResponseFailureHandler())
         .then((response) => response.body as TimelineResponse)
@@ -112,6 +113,7 @@ export class TimelineTestService extends FtrService {
     return await this.supertest
       .patch(TIMELINE_URL)
       .set('kbn-xsrf', 'true')
+      .set('elastic-api-version', '2023-10-31')
       .send({
         timelineId,
         version,
@@ -126,6 +128,7 @@ export class TimelineTestService extends FtrService {
     await this.supertest
       .delete(TIMELINE_URL)
       .set('kbn-xsrf', 'true')
+      .set('elastic-api-version', '2023-10-31')
       .send({
         savedObjectIds: Array.isArray(id) ? id : [id],
       })