Bump external/usersim from 46c6b4a to ca8f2de (microsoft#3782)

Bumps [external/usersim](https://github.com/microsoft/usersim) from `46c6b4a` to `ca8f2de`.
- [Commits](microsoft/usersim@46c6b4a...ca8f2de)

---
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>