Remove unneeded getsym method

Author: penelopeysm

src/varname.jl

@@ -41,6 +41,3 @@ Possibly existing indices of `varname` are neglected.
 ) where {s,missings,_F,_a,_T}
     return s in missings
 end
-
-# HACK: Type-piracy. Is this really the way to go?
-AbstractPPL.getsym(::AbstractVector{<:VarName{sym}}) where {sym} = sym