Update distroless.md (#23259)

`###` should be `##`

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## Description

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## Related issues or tickets

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## Reviews

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- [ ] Technical review
- [ ] Editorial review
- [ ] Product review

Author: tadashi0713

content/manuals/dhi/core-concepts/distroless.md

@@ -17,7 +17,7 @@ Images](../../docker-hub/image-library/trusted-content.md#verified-publisher-ima
 follow similar best practices for minimalism and security but may not be as
 stripped down to ensure compatibility with a wider range of use cases.
 
-### What are minimal or distroless images?
+## What are minimal or distroless images?
 
 Traditional container images include a full OS, often more than what is needed
 to run an application. In contrast, minimal or distroless images include only:
@@ -36,7 +36,7 @@ They typically exclude:
 Docker Hardened Images are based on this model, ensuring a smaller and more
 secure runtime surface.
 
-### What you gain
+## What you gain
 
 | Benefit                | Description                                                                   |
 |------------------------|-------------------------------------------------------------------------------|
@@ -45,7 +45,7 @@ secure runtime surface.
 | Improved security      | Lack of shell and package manager limits what attackers can do if compromised |
 | Better compliance      | Easier to audit and verify, especially with SBOMs and attestations            |
 
-### Addressing common tradeoffs
+## Addressing common tradeoffs
 
 Minimal and distroless images offer strong security benefits, but they can
 change how you work with containers. Docker Hardened Images are designed to
@@ -60,7 +60,7 @@ maintain productivity while enhancing security.
 By balancing minimalism with practical tooling, Docker Hardened Images support
 modern development workflows without compromising on security or reliability.
 
-### Best practices for using minimal images
+## Best practices for using minimal images
 
 - Use multi-stage builds to separate build-time and runtime environments
 - Validate image behavior using CI pipelines, not interactive inspection