Remove unused `git_casing` Rake task
We've had !329 (closed) open for quite some time to run this properly, but we can't keep it because it's unrealistic given all the /mf2/ content that may have compliant names.
We've had !329 (closed) open for quite some time to run this properly, but we can't keep it because it's unrealistic given all the /mf2/ content that may have compliant names.