Delete a superfluous case for MetaItem
MetaSeq's definition makes this unnecessary
> &nbsp;&nbsp; | IDENTIFIER `=` LITERAL
> &nbsp;&nbsp; | IDENTIFIER `(` LITERAL `)`
> &nbsp;&nbsp; | IDENTIFIER `(` _MetaSeq_ `)`
-> &nbsp;&nbsp; | IDENTIFIER `(` _MetaItem_ `,` _MetaSeq_ `)`
>
> _MetaSeq_ :
> &nbsp;&nbsp; &nbsp;&nbsp; EMPTY
