Bump external/bpf_conformance from cfec46b to 68a9fda

Bumps [external/bpf_conformance](https://github.com/Alan-Jowett/bpf_conformance) from `cfec46b` to `68a9fda`.
- [Release notes](https://github.com/Alan-Jowett/bpf_conformance/releases)
- [Commits](Alan-Jowett/bpf_conformance@cfec46b...68a9fda)

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

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