remove docker prune before pulling images

[rochdev]

Motivation

Running docker prune takes 5+ minutes, so we should instead use larger machines with more storage to run scenarios that need more space. Ideally we'd use smaller Docker images, but some of them are really difficult to reduce the size of as the software on them is large to begin with.

Fixes regression from DataDog/dd-trace-js#5884

Changes

Remove docker prune before pulling images.

Workflow

1. ⚠️ Create your PR as draft ⚠️
2. Work on you PR until the CI passes
3. Mark it as ready for review
   • Test logic is modified? -> Get a review from RFC owner.
   • Framework is modified, or non obvious usage of it -> get a review from R&P team

🚀 Once your PR is reviewed and the CI green, you can merge it!

🛟 #apm-shared-testing 🛟

Reviewer checklist

• If PR title starts with [<language>], double-check that only <language> is impacted by the change
• No system-tests internal is modified. Otherwise, I have the approval from R&P team
• A docker base image is modified?
  • the relevant build-XXX-image label is present
• A scenario is added (or removed)?
  • Get a review from R&P team