To remove any Xray Issue Type from your Boards, you need to head into the Board settings:
Select the Edit Filter Query option:
Finally, either remove Xray Issue Types or only include the non-Xray Issue Types:
project = XXX AND issuetype not in (Precondition,Test,"Test Execution","Test Plan","Test Set","Sub Test Execution")
project = XXX AND issuetype in (Bug,Story,Epic,Task,Subtask,Sub-Bug)