tests: py: Properly fix JSON equivalents for netdev/reject.t

tests: py: Properly fix JSON equivalents for netdev/reject.t

Revert commit d1a7b9e19fe65 ("tests: py: update netdev reject test
file"), the stored JSON equivalents were correct in that they matched
the standard syntax input.

In fact, we missed a .json.output file recording the expected deviation
in JSON output.

Fixes: d1a7b9e19fe65 ("tests: py: update netdev reject test file")
Fixes: 7ca3368cd7575 ("reject: Unify inet, netdev and bridge delinearization")
Signed-off-by: Phil Sutter <phil@nwl.cc>
Reviewed-by: Pablo Neira Ayuso <pablo@netfilter.org>