Revert "Scan image vulnerabilities after building the container (script)"

This reverts commit b7a9223d.

Due to lack on testing when only building containers, not pushing the images makes trivy fail. Revert and fix as it is inpacting pipelines.

Closes: #6 (closed)

@rbritoda suggested to make a flag as optional, if we are to do this, then we just use the gitlab own scanning templates (we just need to update docs) as it requires input from user itself.