Revert "Merge branch 'perf/lazy-open-serve' into 'master'"

What does this MR do?

Reverts perf: open files lazily when serving content (!803 - merged) as noted as the root cause for gitlab-com/gl-infra/production#7438 (comment 1027229805)

TODO

• I added the Changelog trailer (e.g. Changelog: added) to the commits that need to be included in the changelog
• I added unit tests or they are not required
• I added acceptance tests or they are not required
• I added documentation (or it's not required)
• I followed code review guidelines
• I followed Go Style guidelines