fix: Update graphQL endpoint configuration to use ChaosGraphQLEndpoint

[r6mez]

Proposed changes

Summary:
Fixes subscriber pod CrashLoopBackOff by ensuring the correct server endpoint is set in the subscriber-config ConfigMap.

Problem:
When users access Litmus UI via localhost, the GraphQL server uses the HTTP Referer header (localhost:8080) to set SERVER_ADDR in the ConfigMap. This results in subscriber pods trying to connect to localhost, which fails inside Kubernetes.

Fix:
Default to http://litmusportal-server-service:9002/query for SERVER_ADDR, ensuring subscribers connect to the correct service in production environments.

Closes: #5369

Types of changes

• New feature (non-breaking change which adds functionality)
• Bugfix (non-breaking change which fixes an issue)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices applies)

Checklist

• I have read the CONTRIBUTING doc
• I have signed the commit for DCO to be passed.
• Lint and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works (if appropriate)
• I have added necessary documentation (if appropriate)

Dependency

Special notes for your reviewer:

[SarthakJain26]

Hi @r6mez, thanks for the PR. Have you tested these changes? Will the user have to make any additional changes when setting up Litmus on local setup? If yes, can you please also document that

[r6mez]

Have you tested these changes? Will the user have to make any additional changes when setting up Litmus on local setup? If yes, can you please also document that

Yes, I have tested it, and it's working fine. The user does not need to do any additional changes; in fact, this fix removes some extra steps in the setup process because of the failure of the subscriber pod