fix(frontend): restrict file explorer to show only .yaml, .yml, .zip, and .tar.gz files

[muzzlol]

Description of your changes:
Restricted the file explorer to only show .yaml, .yml, .zip, and .tar.gz files instead of all files when selecting pipeline files to improve user experience.

Checklist:

• The title for your pull request (PR) follows our title convention
• You have signed off your commits

[google-oss-prow]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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[google-oss-prow]

Hi @muzzlol. Thanks for your PR.

I'm waiting for a kubeflow member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[muzzlol]

A lot of validation checks for file types can now be removed from the codebase. I can make those changes, but i feel like i should get confirmation before that. sorry im kinda new to this.

[hbelmiro]

/ok-to-test

[github-actions]

Approvals successfully granted for pending runs.