feat: remove JobDB extension
This PR removes the LHCb JobDB extension, which is purely there for storing the "RunNumber" field in the Jobs table. From what I can understand by scanning the code, it's inserted at job creation time and only read by the WebApp for display.
This PR does not remove RunNumber
from the Workflow (so not from the XML and not from the JDL).
BEGINRELEASENOTES
*Subsystem CHANGE: remove extension of JobDB
ENDRELEASENOTES