Build(deps): Bump third_party/ibex from 87dfd07 to a05d4d8

Bumps [third_party/ibex](https://github.com/lowRISC/ibex) from `87dfd07` to `a05d4d8`.
- [Commits](lowRISC/ibex@87dfd07...a05d4d8)

---
updated-dependencies:
- dependency-name: third_party/ibex
  dependency-type: direct:production
...

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