fix: inconsistent Milvus hostname default values in README

[pratik-naik003]

Problem

There is a discrepancy in the default hostname provided for Milvus in the README.md file.

In the Environment Variables table, the default value for MILVUS_HOST is documented as:
my-release-milvus.docs-agent.svc.cluster.local

However, in the Pipeline Parameters table immediately below it, the default value for milvus_host is documented as:
milvus-standalone-final.docs-agent.svc.cluster.local

This inconsistency can cause confusion for developers trying to configure the pipeline and connect it to the Milvus instance.

Proposed fix

Unify the default hostname across both tables so they reference the exact same default Milvus service name (e.g., standardizing on my-release-milvus.docs-agent.svc.cluster.local since it matches the provided Helm chart installation command in the README).

Acceptance criteria

• The MILVUS_HOST environment variable and milvus_host pipeline parameter have matching default values in the documentation.
• The chosen default value aligns logically with the provided Helm installation instructions.

[pratik-naik003]

/assign @pratik-naik003