[lld] [lld/ELF] Remove transitionary -plugin-opt=opaque-pointers flag (PR #65529)

[Matthias Braun via llvm-commits]

MatzeB wrote:

Should also remove the equivalent here then: https://github.com/llvm/llvm-project/blob/main/llvm/tools/gold/gold-plugin.cpp#L311

https://github.com/llvm/llvm-project/pull/65529