File tree decorations are misaligned

Created by: felixfbecker

File tree decorations are not aligned properly anymore (vertically and horizontal layout).

Don't know how important it is to prioritize this regression with the deprecation of extensions, but wanted to file in case there are customers that rely on e.g. the Codecov extension and that will keep the feature flag on. It may be a quick fix.

E.g. https://sourcegraph.com/github.com/sourcegraph/sourcegraph@main/-/tree/client/search-ui/src/results/sidebar

/cc @muratsu @jjinnii @ryankscott