Clean up factory arguments in ms-sites group.

* Arguments for user, path, and title are only necessary when we need to do something with those arguments later. Most cases in the ms-sites group do not require them.
* In `test_get_blog_id_from_url_is_case_insensitive()`, we should pass a lowercase domain argument.
* A user factory in `test_switch_restore_blog()` is not necessary.

See #30080

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