[milvus] Add podLabels option for attu.

[brandonschabell]

What this PR does / why we need it:

This adds the ability to add pod labels to pods created as part of the attu deployment.

Checklist

• Chart Version bumped
• Title of the PR starts with chart name (e.g. [mychartname])
• PR only contains changes for one chart

[sre-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: brandonschabell
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[sre-ci-robot]

Welcome @brandonschabell! It looks like this is your first PR to milvus-io/milvus-helm 🎉

[LoveEachDay]

@brandonschabell We'll archive this repo. Could you raise a pr at https://github.com/zilliztech/milvus-helm?

[brandonschabell]

@LoveEachDay No problem, just created PR #1 here: zilliztech/milvus-helm#1 :)