t5321: 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 <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: bk2204

t/t5321-pack-large-objects.sh

@@ -10,8 +10,8 @@ test_description='git pack-object with "large" deltas
 . "$TEST_DIRECTORY"/lib-pack.sh
 
 # 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)
 
 test_expect_success 'setup' '
 	clear_packs &&