Bump external/usersim from ef585ae to 651d2f9 (#3662)

Bumps [external/usersim](https://github.com/microsoft/usersim) from `ef585ae` to `651d2f9`.
- [Commits](microsoft/usersim@ef585ae...651d2f9)

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

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