build(deps): bump third_party/ibex from f30e84b to fe84d64

Bumps [third_party/ibex](https://github.com/lowRISC/ibex) from `f30e84b` to `fe84d64`.
- [Commits](lowRISC/ibex@f30e84b...fe84d64)

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

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