ceph-object-corpus: prune some old releases

We do not need to test these old object encodings as they are covered by
later object collections.

Signed-off-by: Sage Weil <sage@inktank.com>

diff --git a/ceph-object-corpus b/ceph-object-corpus
index 84a153afa71c4468c7a3d78270af6415d0a1c3e7..d9870cdfd89d0d1b791bfc23dce3f263d3214370 160000 (submodule)
--- a/ceph-object-corpus
+++ b/ceph-object-corpus
@@ -1 +1 @@
-Subproject commit 84a153afa71c4468c7a3d78270af6415d0a1c3e7
+Subproject commit d9870cdfd89d0d1b791bfc23dce3f263d3214370