Adds help path for LFS detail on Usage Quotas

What does this MR do and why?

Adds help icon and help page link to project Usage Quotas page.

Related to #418788

Screenshots or screen recordings

Before	After

Link leads to http://127.0.0.1:3000/help/user/project/repository/reducing_the_repo_size_using_git#repository-cleanup

How to set up and validate locally

Open a project Usage Quotas page (e.g. http://127.0.0.1:3000/gitlab-org/gitlab-test/-/usage_quotas#storage-quota-tab)

And verify that the (?) icon is in the place and links proper page.

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.