Remove all font ligatures

What does this MR do and why?

Closes #1781 (closed).

Screenshots, screen recordings, or links to review app

before	after

• Before: https://docs.gitlab.com/ee/user/application_security/continuous_vulnerability_scanning/#configuration

• After: https://1781-remove-ligatures.docs.gitlab-review.app/ee/user/application_security/continuous_vulnerability_scanning/#configuration

• Before: https://docs.gitlab.com/ee/user/project/canary_deployments.html#advanced-traffic-control-with-canary-ingress

• After: https://1781-remove-ligatures.docs.gitlab-review.app/ee/user/project/canary_deployments.html#advanced-traffic-control-with-canary-ingress

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Configure a local GitLab Docs environment: https://gitlab.com/gitlab-org/gitlab-docs/-/blob/main/doc/setup.md.
2. Look at a page that has a word that contains fi in it (e.g, anything about configuration). The letters fi are no longer connected with a ligature.

Merge request acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this merge request.

Closes #1781 (closed)