Release CI fails when resource doesn't have "upstream source"

[sed-i]

In script-exporter (vm charm), we have a file resource,

resources:
  script-exporter-binary:
    type: file
    description: Binary for Script Exporter
    filename: script_exporter

so CI keeps failing with KeyError: 'upstream-source'.

[lucabello]

I wonder if we should modify the charm to use a snap instead of loading the binary as a resource; in any case, that would be a separate issue: canonical/script-exporter-operator#31

We should probably modify the CI (or specifically noctua) to look at the type: of resource, and only look for upstream-source for type: oci-image.