chore(ci): fix e2e's artifact name

[pmalek]

What this PR does / why we need it:

Fix the issue that occurred in https://github.com/Kong/kubernetes-ingress-controller/actions/runs/12156398089/job/33900270172#step:13:19.

The culprit is that when workflow fails, KONG_IMAGE_ARTIFACT is not set so there's a duplicated artifact name across tests against released and unreleased Kong.

[team-k8s-bot]

E2E (targeted) tests with KIND-based clusters were started at https://github.com/Kong/kubernetes-ingress-controller/actions/runs/12157169845

[team-k8s-bot]

E2E (targeted) tests with KIND-based clusters were started at https://github.com/Kong/kubernetes-ingress-controller/actions/runs/12157490093

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.7%. Comparing base (fbfdbeb) to head (6dd7bdb).
Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #6768     +/-   ##
=======================================
- Coverage   79.9%   77.7%   -2.3%     
=======================================
  Files        207     207             
  Lines      24588   24599     +11     
=======================================
- Hits       19665   19120    -545     
- Misses      3925    4500    +575     
+ Partials     998     979     -19     

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[team-k8s-bot]

E2E (targeted) tests with KIND-based clusters were started at https://github.com/Kong/kubernetes-ingress-controller/actions/runs/12157983914

[pmalek]

The artifact issue has been resolved.

https://github.com/Kong/kubernetes-ingress-controller/actions/runs/12157983914/job/33905204636#step:13:3

TestDeployAllInOneDBLESS seem to fail but that's unrelated, I've created #6769 to track this.