doc: fix formatting in mirroring task

[msahihi]

Description

Corrected improper formatting in bash code snippets within the Creating a default routing policy and Mirroring traffic to httpbin-v2 sections. Previously, copy-pasting these snippets would result in parsing errors like

error: error parsing STDIN: error converting YAML to JSON: yaml: line 6: did not find expected key. 

This prevents users from directly using the provided examples.

This PR ensures the commands are directly usable.

Reviewers

• [ ] Ambient
• [x] Docs
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• [ ] Networking
• [ ] Performance and Scalability
• [ ] Extensions and Telemetry
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• [ ] Test and Release
• [ ] User Experience
• [ ] Developer Infrastructure
• [ ] Localization/Translation