libexecinfo: Enable backtrace_test.backtrace_fmt_basic on amd64 again

Due to unwind tables generation enabled after c969310c for csu.

PR:			241562, 246322, 246537
Reviewed by:		kib, ngie
Differential Revision:	https://reviews.freebsd.org/D40758

contrib/netbsd-tests/lib/libexecinfo/t_backtrace.c

@@ -151,11 +151,6 @@ ATF_TC_HEAD(backtrace_fmt_basic, tc)
 
 ATF_TC_BODY(backtrace_fmt_basic, tc)
 {
-#if defined(__amd64__)
-	if (atf_tc_get_config_var_as_bool_wd(tc, "ci", false))
-		atf_tc_skip("https://bugs.freebsd.org/246537");
-#endif
-
 	myfunc(12);
 
 	if (prevent_inline)