chore(postgres): enlarge the postgres volume

[mfocko]

Also resized the stage for the testing purposes, it ain't much(, but it's an honest work), if we reserve a lot of resources on preprod, we can relax it (we're using barely 300MB on stage).

Turns out that you, indeed, can resize the PVC with the pod running and then just rescale the deployment (postgres).

Fixes #604

[softwarefactory-project-zuul[bot]]

Build succeeded. https://softwarefactory-project.io/zuul/t/packit-service/buildset/0fdc63b5f4dc43faabce4f0ea7502b00

:heavy_check_mark: pre-commit SUCCESS in 1m 39s