Replace all old docker "dspace-7_x" tags with "latest" on main

[tdonohue]

References

• Follow-up to GitHub Actions: Split Docker images into separate jobs to run in parallel. Enable 'latest' tag. (for dspace-angular) #2359

Description

Currently, our Docker scripts on main are still referencing the dspace-7_x tagged Docker images. However in #2359, we updated main branch to generate Docker images with the latest tag. (The dspace-7_x tag in DockerHub is to be used for the dspace-7_x branch in GitHub.)

In other words:

• main branch in GitHub should always use latest tag in DockerHub
• dspace-7_x branch in GitHub should always use dspace-7_x tag in DockerHub

This PR ensures that our Docker scripts on main are always referencing the tag latest from DockerHub. (This ensures that main isn't accidentally using Docker images from our dspace-7_x brach)

(Corresponding PR was submitted to backend as well: DSpace/DSpace#8974)

Instructions for Reviewers

• Assuming Docker images build properly, then this is ready to merge. I've tested it locally to ensure local builds from main now use latest images from DockerHub.

[tdonohue]

Merging immediately as this is required for Docker to continue to work proper on main. All test Docker builds worked (see automated checks)