Stop running non-voting oslo.db-python33 in gate

gate-oslo.db-python33 is non-voting so no reason to run it in the gate.
Currently in elastic-recheck we have way to detect if a job is voting or
not, so remove this job so it doesn't appear as a 'bug'.

Change-Id: I7e51488f2b6392f9293f1367015d8fe6d7d6efd0
Related-Bug: #1367799
Merge "Stop running non-voting oslo.db-python33 in gate"