[milvus] Update references to old repo to new zilliztech repo.

[brandonschabell]

What this PR does / why we need it:

Several references to the old repo were still present, so this PR updates those references.

Checklist

• [x] Chart Version bumped
• [x] Variables are documented in the README.md
• [x] Title of the PR starts with chart name (e.g. [mychartname])
• [x] PR only contains changes for one chart