Remove the erased argument check from CaseBuilder
Remove the erased argument check from CaseBuilder

This is done elsewhere, and now just gives a meaningless error on
overlapping cases in some circumstances, so best removed.
(But we do need to find a way to warn on obviously overlapping cases!)

mmhelloworld/idris-jvm,mmhelloworld/idris-jvm,mmhelloworld/idris-jvm,mmhelloworld/idris-jvm,mmhelloworld/idris-jvm,mmhelloworld/idris-jvm