t1400: drop debug `echo` to actually execute `test`

Instead of running `test "foo" = "$(bar)"`, we prefix the whole thing with `echo`. Comparing to nearby tests makes it clear that this is just debug leftover. This line has actually been modified four times since it was introduced in e52290428b (General ref log reading improvements., 2006-05-19) and the `echo` has always survived. Let's finally drop it. This script could need some more cleanups. This is just an immediate fix so that we actually test what we intend to. All other hits for `git grep "\<echo test " -- t/` seem fine. They want to create some input or expected output data. Signed-off-by: Martin Ågren <martin.agren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>