Updated juniper.mdx page for Magic WAN integration with Juniper SRX Firewalls (#18603)

* Updated Juniper SRX docs for Magic WAN

* Lots of changes

* Apply suggestions from code review

Co-authored-by: hyperlint-ai[bot] <154288675+hyperlint-ai[bot]@users.noreply.github.com>

* Apply suggestions from code review

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Co-authored-by: marciocloudflare <[email protected]>
Co-authored-by: hyperlint-ai[bot] <154288675+hyperlint-ai[bot]@users.noreply.github.com>

Author: 3 people