Bump external/libbtf from 5ae35c7 to ab8d59b

Bumps [external/libbtf](https://github.com/Alan-Jowett/libbtf) from `5ae35c7` to `ab8d59b`.
- [Release notes](https://github.com/Alan-Jowett/libbtf/releases)
- [Commits](Alan-Jowett/libbtf@5ae35c7...ab8d59b)

---
updated-dependencies:
- dependency-name: external/libbtf
  dependency-type: direct:production
...

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