Fixed merge request fill tree not respecting fluid width

Phil Hughesrequested to merge
mr-file-tree-inline-fluid-width-fix into master

What does this MR do?

This fixes a bug where the merge request tree toggle would not respect the users fluid width preference.

What are the relevant issue numbers?

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/52916

Does this MR meet the acceptance criteria?

Merge request reports