The test files used in Issue763MultiRepo.java are signed using MD5, which
is now considered invalid. So if that test is run on any recent Java, it
will fail with a signature error. This updates the test files to be signed
with SHA1 instead.
* index.microg.jar is a new version fetched from https://microg.org
* index.antox.jar was resigned with the testy.at.or.at key, since antox
website doesn't exist anymore.
