Fix parameter shadow in DownloadCacheCleaner

[Matyrobbrt]

During the 1.20.4 port both the in path parameter and the parameter of the anonymous class method in vacuumCacheDir were named path therefore leading to the outer variable being shadowed by the inner one.

[sciwhiz12]

Making a validator for this kind of error is going to be painful, and possibly requires some rethinking of the design of our toolchain.

For now, hotfix!