pw_kvs: Remove unused working buffer
pw_kvs: Remove unused working buffer

Removed the KVS working buffer that is not being used. It looks like
this is not needed anymore.

Change-Id: Iec4e87353fa13b1f7fee2a1497187d48b2252215

google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed