Update Markdown Syntax for URL in Header

[0xwitty]

Problem

The URL in the header for the class hash documentation is incorrectly formatted. The current syntax:

:class-hash-cairo-version: \
https://crates.io/crates/cairo-lang-compiler/{cmp_version}[cairo {cmp_version}]

is not valid Markdown for embedding a link.

Solution

The link syntax has been updated to properly follow Markdown standards:

:class-hash-cairo-version: https://crates.io/crates/cairo-lang-compiler/{cmp_version} [cairo {cmp_version}]

Importance

• Clarity: Correctly formatted links ensure that users can click and access the intended documentation without confusion.
• Professionalism: Proper formatting enhances the readability and usability of generated documentation.
• Functionality: A malformed link can break automated tools that parse or render the documentation.

This small change significantly improves the quality of the generated documentation and aligns it with standard practices.

PR Checklist

• Tests
• Documentation
• Added entry to CHANGELOG.md
• Tried the feature on a public network