netbsd-tests: Update a test case to chase grep symlink handling changes

This test case verifies that grep detects symlink loops when traversing
a directory hierarchy.

Fixes:		fc12c191c0 ("grep: Default to -p instead of -S.")
Reviewed by:	ngie, jhb
Reported by:	Jenkins
MFC after:	2 weeks
Differential Revision:	https://reviews.freebsd.org/D46544

contrib/netbsd-tests/usr.bin/grep/t_grep.sh

@@ -81,7 +81,7 @@ recurse_symlink_body()
 
 	atf_check -o file:"$(atf_get_srcdir)/d_recurse_symlink.out" \
 	    -e file:"$(atf_get_srcdir)/d_recurse_symlink.err" \
-	    grep -r string test
+	    grep -rS string test
 }
 
 atf_test_case word_regexps