Minor fixes to Gateway API conformance on release tag

[sunjayBhatia]

• Don't build/load contour image to kind as we should be using the image we just pushed
• Fill in Gateway API version from our environment var

[sunjayBhatia]

noticed when looking at logs for https://github.com/projectcontour/contour/actions/runs/6632046855/job/18017005554

[sunjayBhatia]

The build in CI on the 1.27.0 rc-1 tag worked and used the right contour version, but it did an extra step to build the local contour and load it into the kind cluster, this change just omits that

[skriss]

I see gatewayAPIVersion: TODO in the report, is that expected?

[sunjayBhatia]

I see gatewayAPIVersion: TODO in the report, is that expected?

yeah, that comes from the suite itself, though maybe we can put in the right version ourselves, I'll push a quick commit

[codecov]

Codecov Report

Merging #5894 (41c5f34) into main (381c2c5) will not change coverage.
The diff coverage is n/a.

Additional details and impacted files

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  Misses       3901     3901           
  Partials      303      303