[Rule Management] Skip Cypress tests on MKI executions (elastic#186122)

## Summary

The
`x-pack/test/security_solution_cypress/cypress/e2e/detection_response/rule_management/rule_details/backfill_group.cy.ts`
test is failing on MKI environments (the periodic pipeline).

This is because the test in order to work need to have a feature flag
enabled. FF are not currently supported on MKI environments, that is why
in this PR we are skipping it from MKI environments by adding
`@skipInServerlessMKI` label to it.

Co-authored-by: Kibana Machine <[email protected]>

x-pack/test/security_solution_cypress/cypress/e2e/detection_response/rule_management/rule_details/backfill_group.cy.ts

@@ -34,7 +34,7 @@ import {
 describe(
   'Backfill groups',
   {
-    tags: ['@ess', '@serverless'],
+    tags: ['@ess', '@serverless', '@skipInServerlessMKI'],
     env: {
       ftrConfig: {
         kbnServerArgs: [