Bump dropshot from 7622dc0 to 64f3a3b (#524)

Bumps [dropshot](https://github.com/oxidecomputer/dropshot) from `7622dc0` to `64f3a3b`.
- [Commits](oxidecomputer/dropshot@7622dc0...64f3a3b)

---
updated-dependencies:
- dependency-name: dropshot
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>