[ADT] Remove MutableArrayRef(std::nullopt_t) (NFC)#150471

kazutakahirata merged 1 commit intollvm:mainllvm/llvm-project:mainfrom

kazutakahirata:cleanup_20250724_ArrayRef_nulloptkazutakahirata/llvm-project:cleanup_20250724_ArrayRef_nulloptCopy head branch name to clipboard