[llvm-objdump,SHT_LLVM_BB_ADDR_MAP,NFC] Use auto && instead of const auto & to...

[llvm-objdump,SHT_LLVM_BB_ADDR_MAP,NFC] Use auto && instead of const auto & to allow moving from BBAddrMap objects. (#79456)

std::move on `const auto &` references is essentially a noop. Changing
to `auto &&` to actually allow moving.