Update version to 2.15

[VaishnaviHire]

Description

How Has This Been Tested?

Screenshot or short clip

Merge criteria

• [ ] You have read the contributors guide.
• [ ] Commit messages are meaningful - have a clear and concise summary and detailed explanation of what was changed and why.
• [ ] Pull Request contains a description of the solution, a link to the JIRA issue, and to any dependent or related Pull Request.
• [ ] 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

[openshift-ci[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: grdryn, mattmahoneyrh

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Needs approval from an approver in each of these files: - ~~[OWNERS](https://github.com/opendatahub-io/opendatahub-operator/blob/incubation/OWNERS)~~ [grdryn,mattmahoneyrh] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment

[VaishnaviHire]

/test opendatahub-operator-e2e