docs: clean up the bootstrap docs and make it consistent (#42712)

## Description

This PR cleans up the bootstrap docs and makes it consistent to rest of
the codebase.

---

**Commit Message:** docs: clean up the bootstrap docs and make it
consistent
**Additional Description:** Cleans up the bootstrap docs and makes it
consistent to rest of the codebase.
**Risk Level:** N/A
**Testing:** CI
**Docs Changes:** N/A
**Release Notes:** N/A

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Signed-off-by: Rohit Agrawal <[email protected]>

Mirrored from https://github.com/envoyproxy/envoy @ 7a185b9ade332f769cf2d2570205baef3c13a80a

Author: update-envoy[bot]