fix: failing batch request due to incorrect partial index

Author: dennisgsmith

api/migrations/schema/V1.55.00__drop_submittal_unique_idx.sql

@@ -0,0 +1,3 @@
+-- There are valid cases where a given alert config will have the same completion date for multiple submittals.
+-- For example, if a measurement submittal is missing and multiple subsequent submittals are created, those would all have the same completion date.
+drop index unique_alert_config_id_submittal_date;