debian: Fix tests during debian packaging

The api response json files used in tests were missing from the sdist
tarball created for package purposes, resulting in test failures.

Related T1137
Related T1138

MANIFEST.in

@@ -4,3 +4,4 @@ include requirements.txt
 include requirements-swh.txt
 include requirements-test.txt
 include version.txt
+recursive-include swh/lister/*/tests/ *.json

[Phabricator Migration user]

Some references in the commit message have been migrated:

• T1137 is now swh/meta#1137 (closed)
• T1138 is now swh/meta#1138 (closed)