[clang] [clang] MangledSymbol: remove pointless copy of vector (PR #90012)

[Shafik Yaghmour via cfe-commits]

shafik wrote:

> Looking at the logs, and the error seems to be unrelated to the changes made https://buildkite.com/llvm-project/clang-ci/builds/16430#018f132d-506e-440c-b18b-fed98237def9/54-5446

You can try using `--allow-empty` to do an empty commit to kick off the build again.

https://github.com/llvm/llvm-project/pull/90012