chore: remove closed issue documentation files

Removed 3 closed issue documentation files from docs/issues/:
- #251: implement-basic-trivy-scanning-workflow
- #253: update-docker-images-to-latest-versions
- #255: add-socket-address-uniqueness-validation

All these issues have been closed on GitHub and no longer need
local documentation files.

Remaining open issues: #241, #250, #252

Author: josecelano