fixed link of k8s design proposals in README

[dev-strender]

The title says it all.

[volcano-sh-bot]

Welcome @dev-strender! It looks like this is your first PR to volcano-sh/devices 🎉

[wangyang0616]

Thanks for your contribution, please make CI happy.
See tips for repair method:

To avoid having PRs blocked in the future, always include Signed-off-by: Author Name <[email protected]> in every commit message. You can also do this automatically by using the -s flag (i.e., git commit -s).

[Thor-wl]

Generally LGTM for me except for the DCO check.

[volcano-sh-bot]

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[dev-strender]

/assign @william-wang