Synchronize DMS-REQ-0274 (Alert Content) with DPDD

In DM-10130 DPDD was updated to indicate only 12 months of lightcurve data would be included in the alert information. Unfortunately in LCR-962 I forgot to tweak the contents of DMS-REQ-0274 to match so it still says:

all previous DIASource records corresponding to the object (if any)

This text needs to be changed and an LCR submitted.