docs: update 05_go.mdx

[alfiepoleon]

ory.FrontendApi changed to ory.FrontendAPI

Related Issue or Design Document

Checklist

• I have read the contributing guidelines and signed the CLA.
• I have referenced an issue containing the design document if my change introduces a new feature.
• I have read the security policy.
• I confirm that this pull request does not address a security vulnerability.
  If this pull request addresses a security vulnerability,
  I confirm that I got approval (please contact security@ory.sh) from the maintainers to push the changes.
• I have added tests that prove my fix is effective or that my feature works.
• I have added the necessary documentation within the code base (if appropriate).

Further comments

[CLAassistant]

All committers have signed the CLA.

[aeneasr]

Awesome, thank you! 🎉 Your contribution makes Ory better :)