docs: update invalid link in readme.md

[tsnob]

This PR:

Corrects the invalid link referred in the readme document. While studying the readme, I found one of the referred link is invalid "docker-compose-demo.yaml", after checking the file structure, I think the correct file mentioned should be "docker-compose.yaml.

This PR does not:

Includes any code changes.

Key places to review:

the new linked file whether it is valid now.

Things tested:

no needs to test as only doc modified

[CLAassistant]

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