testsuite/interface-stability: normalise versions

This eliminates spurious changes from version bumps.

testsuite/tests/interface-stability/all.T

 def check_package(pkg_name):
     test(f'{pkg_name}-exports',
-         req_hadrian_deps(['test:dump-decls']),
+         [req_hadrian_deps(['test:dump-decls']),
+          normalise_version(pkg_name),
+         ],
          makefile_test,
          [f'exports_{pkg_name}'])