fix(ui): remove _lastModified workaround from timestamp bump utils

[manaswinidas]

Description

The MR API previously had a bug where PATCH calls didn't always update lastUpdateTimeSinceEpoch for RegisteredModels and ModelVersions. A workaround was added in the frontend that injected a _lastModified custom property into the PATCH body to force a timestamp update.

Now that the backend correctly updates lastUpdateTimeSinceEpoch on every PATCH call (via the generic repository Save method), this workaround is no longer needed.

Changes

• Removed the customProperties object (including _lastModified) from bumpModelVersionTimestamp and bumpRegisteredModelTimestamp in updateTimestamps.ts. Both now send only { state: ModelState.LIVE }.
• Updated tests to match the simplified behavior and removed tests that specifically verified the workaround's customProperties spreading.
• Updated the comment on the _lastModified filter in getProperties (utils.ts) to reflect it's now a legacy filter. The filter is intentionally kept so existing models don't suddenly show a confusing _lastModified property after upgrade.

How Has This Been Tested?

• Ran updateTimestamps.test.ts — all 8 tests pass
• Ran utils.spec.ts — all 66 tests pass (including the _lastModified filter test)

To verify end-to-end: edit the details of a ModelVersion (e.g. change its description, labels, or properties) and verify that its associated RegisteredModel has its last modified time updated and appears at the top of the list when sorting by last modified time.

Merge criteria:

• All the commits have been signed-off (To pass the DCO check)

• The commits have meaningful messages

• Automated tests are provided as part of the PR for major new functionalities; testing instructions have been added in the PR body (for PRs involving changes that are not immediately obvious).

• The developer has manually tested the changes and verified that the changes work.

• Code changes follow the kubeflow contribution guidelines.

• For first time contributors: Please reach out to the Reviewers to ensure all tests are being run, ensuring the label ok-to-test has been added to the PR.

If you have UI changes

• The developer has added tests or explained why testing cannot be added.
• Included any necessary screenshots or gifs if it was a UI change.
• Verify that UI/UX changes conform the UX guidelines for Kubeflow.

[manaswinidas]

/retest

[ppadti]

/retest

[ppadti]

/lgtm
/approve

[google-oss-prow]

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[ppadti]

/lgtm