Fix various Rust documentation formatting issues

[samscott89]

Summary

Related issue: #23649.

Found the Rust code samples that were formatting incorrectly and fixed them. Also tried to fix the spacing around
some of the code blocks with Tab components because in my experience that's where prettier can sometimes get confused.

Documentation checklist

• The documentation style guide has been adhered to.
• If a larger change - such as adding a new page- an issue has been opened in relation to any incorrect or out of date information that this PR fixes.
• Files which have changed name or location have been allocated redirects.

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PR Change Summary

Fixed various formatting issues in Rust documentation across multiple examples.

• Corrected formatting of Rust code samples for consistency.
• Adjusted spacing around code blocks to improve readability.
• Ensured adherence to the documentation style guide.

Modified Files

• src/content/docs/workers/examples/basic-auth.mdx
• src/content/docs/workers/examples/cors-header-proxy.mdx
• src/content/docs/workers/examples/logging-headers.mdx
• src/content/docs/workers/examples/security-headers.mdx
• src/content/docs/workers/examples/websockets.mdx

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[samscott89]

FYI this blank space is what prevents (I think) prettier from treating the code block as markdown code which is what leads to it mangling the code.