.github,test: Rename the ARTIFACTS_DIR variable to ARTIFACT_DIR

[timflannagan]

Signed-off-by: timflannagan timflannagan@gmail.com

Description of the change:
Fix the ARTIFACTS_DIR variable and rename that to the proper ARTIFACT_DIR variable so OLM can work on prow-based CI environments.

Motivation for the change:
Maintain consistency with the various CI platforms (e.g. prow)

Reviewer Checklist

• Implementation matches the proposed design, or proposal is updated to match implementation
• Sufficient unit test coverage
• Sufficient end-to-end test coverage
• Docs updated or added to /doc
• Commit messages sensible and descriptive
• Tests marked as [FLAKE] are truly flaky
• Tests that remove the [FLAKE] tag are no longer flaky

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: timflannagan

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [timflannagan]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[dinhxuanvu]

/lgtm