fix: use the new genai docker repo

[tayritenour]

Description

This uses the new genai docker repo rather than the older repo we were using before.

Test Plan

Deploy a determined cluster on AWS. Example:

det deploy aws up \
    --deployment-type genai \
    --genai-version latest \
    --det-v 0.27.0 \
    --aux-agent-instance-type m5.large \
    --compute-agent-instance-type g4dn.xlarge

With your own cluster-id and keypair.

SSH into the master and confirm the docker image is from determinedai/genai:latest rather than determinedai/environments-dev:lore-backend-image-latest

Commentary (optional)

Checklist

• Changes have been manually QA'd
• User-facing API changes need the "User-facing API Change" label.
• Release notes should be added as a separate file under docs/release-notes/.
  See Release Note for details.
• Licenses should be included for new code which was copied and/or modified from any external code.

Ticket

[netlify]

✅ Deploy Preview for determined-ui canceled.

Name	Link
🔨 Latest commit	767038c
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[codecov]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (d661404) 47.28% compared to head (767038c) 47.28%.
Report is 7 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8745      +/-   ##
==========================================
- Coverage   47.28%   47.28%   -0.01%     
==========================================
  Files        1045     1045              
  Lines      166788   166788              
  Branches     2246     2246              
==========================================
- Hits        78862    78861       -1     
- Misses      87768    87769       +1     
  Partials      158      158              

Flag	Coverage Δ
backend	40.93% <ø> (-0.01%)	⬇️
harness	64.35% <0.00%> (ø)
web	42.57% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
...ness/determined/deploy/aws/deployment_types/vpc.py	54.28% <0.00%> (ø)

... and 3 files with indirect coverage changes

[ioga]

Suggested change

	"determinedai/genai:${GenAIVersion}"
	"${ImageRepoPrefix}/genai:${GenAIVersion}"