build(deps): bump llvm-project from 91ca2e1 to 2b2e860

Bumps [llvm-project](https://github.com/Xilinx/llvm-project) from `91ca2e1` to `2b2e860`.
- [Commits](Xilinx/llvm-project@91ca2e1...2b2e860)

---
updated-dependencies:
- dependency-name: llvm-project
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>