testing/komikku: downgrade to 1.39.0

This reverts commit 1726afbe.

Unfortunately, I failed to notice, that version 1.41.1 (!63439 (merged)) introduced a new dependency on py3-curl_cffi. It wasn't listed in the release notes, and I apparently forgot to install the app, or didn't properly install it. (It could also be that I tested 1.41.0 or 1.40.0 which worked, but decided to upgrade to a newer version in the same go)

I've verified that this version works and would like to downgrade komikku back to 1.39.0, until I find a solution to !63915 (merged).

However, I don't know if this is possible at all.