t5309: make test hash independent

Use the proper pack constants defined in lib-pack.sh to make this test
work with SHA-256.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t5309-pack-delta-cycles.sh

@@ -4,15 +4,9 @@ test_description='test index-pack handling of delta cycles in packfiles'
 . ./test-lib.sh
 . "$TEST_DIRECTORY"/lib-pack.sh
 
-if ! test_have_prereq SHA1
-then
-       skip_all='not using SHA-1 for objects'
-       test_done
-fi
-
 # Two similar-ish objects that we have computed deltas between.
-A=01d7713666f4de822776c7622c10f1b07de280dc
-B=e68fe8129b546b101aee9510c5328e7f21ca1d18
+A=$(test_oid packlib_7_0)
+B=$(test_oid packlib_7_76)
 
 # double-check our hand-constucted packs
 test_expect_success 'index-pack works with a single delta (A->B)' '