manage-debug-suites: remove sourceless binaries too

For unstable dak adds the source package to the debug suite, but we
don't do that for testing (though dak will ensure the source is
present and keep it as an extra source in the Sources index).

This change makes sure to also remove obsolete debug packages that had
no source in the debug suite.

dak/manage_debug_suites.py

@@ -76,7 +76,7 @@ def clean(debug_suite, transaction):
      USING binaries b
      WHERE ba.suite = :debugsuite_id
        AND ba.bin = b.id
-       AND b.source IN (SELECT source FROM sources_removed)
+       AND b.source NOT IN (SELECT source FROM sources_to_keep)
     RETURNING
       b.package,
       b.version,