[ELF] - Remove dead code.

I do not think this code was ever alive,
because the following code says we can have OutputSection and
SymbolAssignment cases only. We already handle both of them.

https://github.com/llvm-mirror/lld/blob/master/ELF/ScriptParser.cpp#L502

FWIW, it is dead in the LLD code coverage reports I am running either.

llvm-svn: 335958