test-lib: turn on GIT_TEST_CHAIN_LINT by default Now that the feature has had time to prove itself, and any topics in flight have had a chance to clean up any broken &&-chains, we can flip this feature on by default. This makes one less thing submitters need to configure or check before sending their patches. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>