[qsharp/en-us] Update qsharp example

[sezna]

• [x] I solemnly swear that this is all original content of which I am the original author
• [x] Pull request title is prepended with [language/lang-code] (example [python/fr-fr] or [java/en])
• [x] Pull request touches only one file (or a set of logically related files with similar changes made)
• [x] Content changes are aimed at intermediate to experienced programmers (this is a poor format for explaining fundamental programming concepts)
• [N/A] If you've changed any part of the YAML Frontmatter, make sure it is formatted according to CONTRIBUTING.md
  • [x] Yes, I have double-checked quotes and field names!

The Q# language has evolved a bit since this example was last updated. This PR updates the example code to compile in the modern compiler, runs the canonical formatter on it, updates the syntax highlighting to the now-supported qsharp syntax highlighter, and updates the references to the latest content we've published.

[verhovsky]

Thank you for working on this

[sezna]

no problem, it was reasonably self-serving 😄 thanks for providing this educational resource.