test: drop test-bin target
test: drop test-bin target

The current default target in test/Makefile is `test-bin` [1] as this is
the first target in the makefile. This was unintentional change
introduced in [2]. The default target should be `all`.

However, `test-bin` does not appear to be used anywhere and thus, we can
remove it.

[1] https://www.gnu.org/software/make/manual/html_node/Rules.html
[2] https://github.com/checkpoint-restore/go-criu/pull/71

Signed-off-by: Radostin Stoyanov <af191057dab5b67c1c1061d181b58b884c4ed7f3@fedoraproject.org>

checkpoint-restore/go-criu,checkpoint-restore/go-criu,checkpoint-restore/go-criu