Bump openssl in /limitador-server/sandbox/loadtest

Bumps [openssl](https://github.com/sfackler/rust-openssl) from 0.10.64 to 0.10.66.
- [Release notes](https://github.com/sfackler/rust-openssl/releases)
- [Commits](sfackler/rust-openssl@openssl-v0.10.64...openssl-v0.10.66)

---
updated-dependencies:
- dependency-name: openssl
  dependency-type: indirect
...

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