DAOS-13957 object: revert object RPC version bump (#12636)

Commit 7010f2e unecessarily bumped the RPC version. Instead of adding back 2 object RPC version support, just revert this version bump for master and 2.4 to keep interop support with 2.2.

Required-githooks: true

Signed-off-by: Mohamad Chaarawi <mohamad.chaarawi@intel.com>

src/object/obj_rpc.h

@@ -31,7 +31,7 @@
  * These are for daos_rpc::dr_opc and DAOS_RPC_OPCODE(opc, ...) rather than
  * crt_req_create(..., opc, ...). See daos_rpc.h.
  */
-#define DAOS_OBJ_VERSION 9
+#define DAOS_OBJ_VERSION 8
 /* LIST of internal RPCS in form of:
  * OPCODE, flags, FMT, handler, corpc_hdlr and name
  */