Add timeout in discover reader in dev-app

[tim-lin-bbpos]

Summary

Add timeout in discover reader in dev-app

Motivation

Add timeout in discover reader for testing purpose https://jira.corp.stripe.com/browse/TERMINAL-40545

Testing

• [x] I tested this manually
• [ ] I added automated tests

Documentation

Select one:

• [ ] I have added relevant documentation for my changes.
• [x] This PR does not result in any developer-facing changes.