These were overlooked in !115.

Change more environment variable references to be Ethima-specific

See merge request !117

The upstream `CI_RENOVATE_IMAGE` environment variable could always be
used to control this. To expose this more directly an additional
variable is introduced. This also enables the process to keep pinning
the version, which has been unpinned as of v20 of the upstream process.

The upstream version of the Renovate template no longer pins the
specific version of Renovate to use and does not generate new releases
based on that. To mimic the previous behavior this process now pins the
version to use instead and needs to keep it up-to-date accordingly.

build(deps): update dependency renovate-bot/renovate-runner to v20

See merge request !109

# [3.1.0](v3.0.1...v3.1.0) (2025-04-23)

### Features

* add project specific environment variable for the used container image ([59b910d2](59b910d2))