fix: Avoid double counting files and folders (#287)

[Vekhir]

@whoozle
Adding the directory to the files list is used to recurse into the subdirectories. The iterator flag QDirIterator::Subdirectories already does that automatically, so we only need to create the directory, not recurse into it.

This line wasn't in the initial implementation, instead was added later in 4b0a921. This PR is basically a revert of that commit. It's an easy mistake to make since the code looks recursive, but actually it's not. The recursion is handled implicitly by the iterator.

Resolves #287