testsuite: drop setgroups unit test

Problem: the diod server checks at runtime whether or not its supplemenatary
group switching strategy works with the kernel hosting the server, but we
also have a unit test that does the same on the build system.

It's a little pointless to test the build system.
Drop that test.

src/libnpfs/Makefile.am

@@ -51,7 +51,6 @@ TESTS = \
 	test_fidpool.t \
 	test_capability.t \
 	test_setfsuid.t \
-	test_setgroups.t \
 	test_setreuid.t
 
 check_PROGRAMS = $(TESTS)
@@ -71,8 +70,5 @@ test_capability_t_LDADD = $(test_ldadd)
 test_setfsuid_t_SOURCES = test/setfsuid.c
 test_setfsuid_t_LDADD = $(test_ldadd)
 
-test_setgroups_t_SOURCES = test/setgroups.c
-test_setgroups_t_LDADD = $(test_ldadd)
-
 test_setreuid_t_SOURCES = test/setreuid.c
 test_setreuid_t_LDADD = $(test_ldadd)