Linker: Always pass RF_IgnoreMissingLocals; NFC

This is a cleanup after clarifying the meaning of RF_IgnoreMissingLocals
in r265628 and truly limiting it to locals in r265768.

This should have no functionality change, since the only context that
the flag has an effect is when we could hit function-local Value and
Metadata, and we were already passing it in those contexts.

llvm-svn: 265831