Remove expected failure from lib.libc.sys.t_mincore:mincore_resid

The failure was added based on observation seen on 11.0-CURRENT @ r273153, not
based on internal testing at EMC/Isilon

PR: 194829
Tested with the following configuration:
- amd64/i386
- 11.0-CURRENT @ r273153
- 100 times in a tight loop as root with the following commands...
-- kyua test lib/libc
-- kyua test lib/libc/sys
-- kyua test lib/libc/sys/mincore_test

contrib/netbsd-tests/lib/libc/sys/t_mincore.c

@@ -206,9 +206,6 @@ ATF_TC_BODY(mincore_resid, tc)
 		    "might be low on memory");
 
 #ifdef __FreeBSD__
-	atf_tc_expect_fail("the following calls fail; this seems to be a new "
-	    "issue (didn't occur in 07/2014)");
-
 	ATF_REQUIRE(mlock(addr, npgs * page) == 0);
 #endif
 	ATF_REQUIRE(check_residency(addr, npgs) == npgs);