Remove blob refactor feature flag references

What does this MR do and why?

Removes references to the refactor_blob_viewer feature flag since the feature flag is enabled by default and we're already removing some of the old code.

Screenshots or screen recordings

No visual changes are expected

Screen_Recording_2022-07-05_at_11.17.07

How to set up and validate locally

View files via the repository browser

MR 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 MR.