Update file to modify in the README when adding a system index (opens…

…earch-project#4139)

### Description

Updates the README to the current location of the default system
indexes.

* Category

Documentation

### Check List
- [ ] New functionality includes testing
- [ ] New functionality has been documented
- [ ] Commits are signed per the DCO using --signoff

By submitting this pull request, I confirm that my contribution is made
under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and
signing off your commits, please check
[here](https://github.com/opensearch-project/OpenSearch/blob/main/CONTRIBUTING.md#developer-certificate-of-origin).

Signed-off-by: Craig Perkins <[email protected]>

README.md

@@ -129,8 +129,7 @@ plugins.security.system_indices.indices: [".plugins-ml-model", ".plugins-ml-task
 
 The demo configuration can be modified in the following files to add a new system index to the demo configuration:
 
-- https://github.com/opensearch-project/security/blob/main/tools/install_demo_configuration.sh
-- https://github.com/opensearch-project/security/blob/main/tools/install_demo_configuration.bat
+- https://github.com/opensearch-project/security/blob/main/src/main/java/org/opensearch/security/tools/democonfig/SecuritySettingsConfigurer.java
 
 
 ## Contributing