This change both speeds up specs (less strings to allocate) and helps catch
cases where methods in Discourse are mutating inputs.
Overall we will be migrating everything to use #frozen_string_literal: true
it will take a while, but this is the first and safest move in this direction
This reduces the number of scans that the db has to do in the query
to fetch orphan uploads. Futheremore, we were not batching our
records which bloats memory.