cpudimm: Remove odata.context

Redfish made odata.context optional (1.6.0 of DSP0266) and
has removed odata.context from example payloads in the
specification (1.7.0 of DSP0266), removed it from the mockups,
and Redfish recommended not using.

Change-Id: I4f9ce00b8cc6f413896879d8c8ec6e093279bd47
Signed-off-by: Gunnar Mills <gmills@us.ibm.com>