Bump third_party/pigweed/repo from 704aebc to 7e48ff5

Bumps [third_party/pigweed/repo](https://github.com/google/pigweed) from `704aebc` to `7e48ff5`.
- [Release notes](https://github.com/google/pigweed/releases)
- [Commits](google/pigweed@704aebc...7e48ff5)

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

Signed-off-by: dependabot[bot] <support@github.com>