Add IP ranges note

[buraizu]

What does this PR do?

Add a note about adding Datadog's IP ranges to an allowlist if using a firewall.

Motivation

DOCS-8007

Review checklist

• [x] PR has a meaningful title or PR has the no-changelog label attached
• [ ] Feature or bugfix has tests
• [ ] Git history is clean
• [x] If PR impacts documentation, docs team has been notified or an issue has been opened on the documentation repo
• [ ] If this PR includes a log pipeline, please add a description describing the remappers and processors.

Additional Notes

Anything else we should know when reviewing?

[buraizu]

/merge

[dd-devflow[bot]]

:steam_locomotive: MergeQueue: pull request added to the queue

The median merge time in master is 0s.

Use /merge -c to cancel this operation!

[dd-devflow[bot]]

:x: MergeQueue: The build pipeline has timeout

The merge request has been interrupted because the build took longer than expected. The current limit for the base branch 'master' is 120 minutes.

If you need support, contact us on Slack #devflow with those details!