HMD Put On/Remove From Head events not implemented

Even though issue 41448 is still marked unresolved, implementation appears to have been dropped in by version 4.17:

https://github.com/EpicGames/UnrealEngine/commit/997ef1594140096b60bf14112b8a62ff0041a44c#diff-3275990b788d682b3bdeb5749636f709R1506

…but I’m currently struggling to get it working in 4.19.2