Minor tweaks after preparing VPA 0.14.0 release.

[kgolab]

What type of PR is this?

/kind cleanup
/kind documentation

What this PR does / why we need it:

Some minor updates to the instructions on how to release VPA, based on the process done under #5851:

• use registry.k8s.io rather than k8s.gcr.io,
• make the copy&paste easier (no need to remove $ manually)
• add a note about add-version.sh script

[k8s-ci-robot]

@kgolab: The label(s) kind/clean-up cannot be applied, because the repository doesn't have them.

In response to this:

What type of PR is this?

/kind clean-up
/kind documentation

What this PR does / why we need it:

Some minor updates to the instructions on how to release VPA:

• use registry.k8s.io rather than k8s.gcr.io,
• make the copy&paste easier (no need to remove $ manually)
• add a note about add-version.sh script

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[jbartosik]

Looks good to me, one small comment, not giving LGTM to avoid merge before you see the comment

[jbartosik]

optional: I'd maybe use stronger wording, I expect the script to be less error prone than humans.
Maybe s/can/should/

[kgolab]

Updated, PTAL.

[mwielgus]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jbartosik, kgolab, mwielgus

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