[rust] fix urls (#1328)

### Description

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### Demo URL

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Provide a URL to a live deployment where we can test your PR. If a demo
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### Type of Change

- [ ] New Example
- [ ] Example updates (Bug fixes, new features, etc.)
- [ ] Other (changes to the codebase, but not to examples)

### New Example Checklist

- [ ] 🛫 `npm run new-example` was used to create the example
- [ ] 📚 The template wasn't used but I carefuly read the [Adding a new
example](https://github.com/vercel/examples#adding-a-new-example) steps
and implemented them in the example
- [ ] 📱 Is it responsive? Are mobile and tablets considered?

Author: ecklf

rust/axum/README.md

@@ -9,7 +9,7 @@ type:
 css:
   - None
 githubUrl: https://github.com/vercel/examples/tree/main/rust/axum
-demoUrl: https://rust-axum.vercel.app
+demoUrl: https://rust-axum.vercel.dev
 deployUrl: https://vercel.com/new/clone?repository-url=https://github.com/vercel/examples/tree/main/rust/axum&project-name=rust-axum&repository-name=rust-axum
 publisher: Vercel
 relatedTemplates:

rust/hello-world/README.md

@@ -9,7 +9,7 @@ type:
 css:
   - None
 githubUrl: https://github.com/vercel/examples/tree/main/rust/hello-world
-demoUrl: https://rust-hello-world.vercel.app
+demoUrl: https://rust-hello-world.vercel.dev
 deployUrl: https://vercel.com/new/clone?repository-url=https://github.com/vercel/examples/tree/main/rust/hello-world&project-name=rust-hello-world&repository-name=rust-hello-world
 publisher: Vercel
 relatedTemplates: