docs: Correct cmd file path for manage configuration in README.md

[rmbrntt]

Type of change (place an x in the [ ] that applies)

• New sample
• New feature
• Bug fix
• Documentation

Summary

README has the command slack trigger create --trigger-def triggers/manage_configuration_trigger.ts which doesn't exist so it throws an error

Actual file path in repo is triggers/manage_configuration_shortcut_trigger.ts

PR updates the command listed in the README to correct location.

Requirements (place an x in each [ ] that applies)

• I’ve checked my submission against the Samples Checklist to ensure it complies with all standards
• I have ensured the changes I am contributing align with existing patterns and have tested and linted my code
• I've read and agree to the Code of Conduct

[salesforce-cla]

Thanks for the contribution! Before we can merge this, we need @rmbrntt to sign the Salesforce Inc. Contributor License Agreement.

[hello-ashleyintech]

🙌 LGTM! Thanks for updating this 😄