[clang] [CIR] Remove cir.unary(plus, ...) and emit nothing for unary plus (PR #185278)

[Henrich Lauko via cfe-commits]

xlauko wrote:

### Merge activity

* **Mar 14, 7:21 PM UTC**: [Graphite](https://app.graphite.com/github/pr/llvm/llvm-project/185278) rebased this pull request as part of a merge.


https://github.com/llvm/llvm-project/pull/185278