[Security Solution][Endpoint][Response Actions] Execute Operations behind FF for 8.7 (#150383)

## Summary

Hides `execute` RBAC control behind FF so that it is not available in
8.7

### Checklist
- [ ] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios

x-pack/test/api_integration/apis/security/privileges_basic.ts

@@ -121,7 +121,6 @@ export default function ({ getService }: FtrProviderContext) {
               'trusted_applications_all',
               'trusted_applications_read',
               'file_operations_all',
-              'execute_operations_all',
             ],
             uptime: ['all', 'read', 'minimal_all', 'minimal_read'],
             securitySolutionCases: ['all', 'read', 'minimal_all', 'minimal_read', 'cases_delete'],