Correct license test results

We now properly detect a CC0-1.0 and not a combo of CC0-1.0 and
public domain

Signed-off-by: Philippe Ombredanne <pombredanne@nexb.com>

Author: pombredanne

tests/licensedcode/data/datadriven/external/licensecheck/devscripts/multi-line-copyright.c.yml

@@ -1,4 +1,3 @@
 license_expressions:
   - gpl-3.0
-  - public-domain
   - cc0-1.0