Bump mockttp from 3.3.1 to 3.4.0 (#719)

* Bump mockttp from 3.3.1 to 3.4.0

Bumps [mockttp](https://github.com/httptoolkit/mockttp) from 3.3.1 to 3.4.0.
- [Release notes](https://github.com/httptoolkit/mockttp/releases)
- [Commits](httptoolkit/mockttp@v3.3.1...v3.4.0)

---
updated-dependencies:
- dependency-name: mockttp
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

* Reformat package-lock.json [dependabot skip]

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