Fix typo on index page

[aschepis]

Proposed changes

Just a simple typo fix in the documentation

Checklist

• I have read the contributing guidelines.
• 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 green light (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 or changed the documentation.

Further comments

[CLAassistant]

All committers have signed the CLA.

[aeneasr]

Awesome 🎉

Thank you for your contribution!