Redundant inputs for triggers involving assessments

[maufcost]

After a quick brainstorm with @FrenjaminBanklin on #1953, we decided to remove the text inputs that ask for assessment ids when creating triggers involving the following assessment actions: Start an attempt for and End an attempt for. They are redundant because Obojobo only allows one assessment per module; therefore, the id can only be one regardless if you change it or not.

[maufcost]

Closing this and reopening #1625 since authors WILL need those inputs in case they create multiple assessments in a module.