[Security Solution][Entity Analytics][PrivMon]Removing unused code (#233963)

## Summary

Removes the unused constant using the `.privmon*` index.
Removes the file declaring an unused privilege for privmon pipelines and
indexes.


### Checklist

Check the PR satisfies following conditions. 

Reviewers should verify this PR satisfies this list as well.

- [ ] [Flaky Test
Runner](https://ci-stats.kibana.dev/trigger_flaky_test_runner/1) was
used on any tests changed
- [ ] The PR description includes the appropriate Release Notes section,
and the correct `release_note:*` label is applied per the
[guidelines](https://www.elastic.co/guide/en/kibana/master/contributing.html#kibana-release-notes-process)
- [ ] Review the [backport
guidelines](https://docs.google.com/document/d/1VyN5k91e5OVumlc0Gb9RPa3h1ewuPE705nRtioPiTvY/edit?usp=sharing)
and apply applicable `backport:*` labels.

Author: abhishekbhatia1710

x-pack/solutions/security/plugins/security_solution/server/lib/entity_analytics/privilege_monitoring/auth/privileges.ts

@@ -24,10 +24,6 @@ export const PRIVILEGE_MONITORING_ENGINE_STATUS = {
   NOT_INSTALLED: 'not_installed',
 } as const;
 
-// Base constants
-export const PRIVMON_BASE_PREFIX = 'privmon' as const;
-export const PRIVILEGE_MONITORING_INTERNAL_INDICES_PATTERN = `.${PRIVMON_BASE_PREFIX}*` as const;
-
 // Indices that are exclude from the search
 export const PRE_EXCLUDE_INDICES: string[] = [
   ...INCLUDE_INDEX_PATTERN.map((index) => `-${index}`),