Problem: Post merge docker push fails (#724)

There are changes in Sigstore's Trusted root used for signing, details
are explained here => https://blog.sigstore.dev/tuf-root-update/

Solution: Switch to cosign-release v2.2.3

Fixes https://github.com/dimitri/pgcopydb/issues/723



Signed-off-by: Arunprasad Rajkumar <ar.arunprasad@gmail.com>