Linked enhancements tracking board in release readme

[sreeram-venkitesh]

What type of PR is this:

/kind documentation

What this PR does / why we need it:

Links the enhancement tracking board for v1.31 release to the v1.31 release's readme file.

Which issue(s) this PR fixes:

None.

Special notes for your reviewer:

CC: @neoaggelos

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: saschagrunert, sreeram-venkitesh

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

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Needs approval from an approver in each of these files: - ~~[releases/release-1.31/OWNERS](https://github.com/kubernetes/sig-release/blob/master/releases/release-1.31/OWNERS)~~ [saschagrunert] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment

[sreeram-venkitesh]

I need to update the link to the feature blog tracking board before merging this PR.

[saschagrunert]

@sreeram-venkitesh you can put a /hold on PR's which should not be merged after approval.

[sreeram-venkitesh]

/hold

[saschagrunert]

@sreeram-venkitesh this PR got already merged, you have to revert those changes to go back to the original state.

[sreeram-venkitesh]

Ah I didn't notice when looking at it from my phone. I can raise another PR for adding the link, it doesn't need to be done in the same PR.