Fix variable reference for agent IP in key vault access

[BalintBanyasz]

The sample currently sets the agentIP variable incorrectly:

echo "##vso[task.setvariable variable=agentIP]ip"

This stores the literal string ip instead of the value of $ip. As a result, the later Remove-AzKeyVaultNetworkRule step cannot remove the rule that was added, leaving the agent IP in the Key Vault network rules.

The sample should only use:

echo "##vso[task.setvariable variable=agentIP]$ip"

Likewise, the removal step should reference the pipeline variable:

$ipRange = "$(agentIP)/32"

This ensures the example works end-to-end.

[prmerger-automator]

@BalintBanyasz : Thanks for your contribution! The author(s) and reviewer(s) have been notified to review your proposed change.

[prmerger-automator]

@BalintBanyasz : Thanks for your contribution! The author(s) and reviewer(s) have been notified to review your proposed change.

[v-regandowner]

@ramiMSFT

Can you review the proposed changes?

IMPORTANT: When the changes are ready for publication, adding a #sign-off comment is the best way to signal that the PR is ready for the review team to merge.

#label:"aq-pr-triaged"
@MicrosoftDocs/public-repo-pr-review-team