Bump mockito from 1.4.0 to 2.0.4

Bumps [mockito](https://github.com/mockito/mockito) from 1.4.0 to 2.0.4.
- [Release notes](https://github.com/mockito/mockito/releases)
- [Commits](https://github.com/mockito/mockito/commits)

---
updated-dependencies:
- dependency-name: mockito
  dependency-version: 2.0.4
  dependency-type: direct:development
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

requirements-dev.txt

@@ -6,7 +6,7 @@
 # Requirements needed for SeleniumLibrary development but not by end users.
 # Creating releases has its own requirements listed in requirements-build.txt.
 invoke == 2.2.0
-mockito == 1.4.0
+mockito == 2.0.4
 robotstatuschecker == 4.1.1
 approvaltests == 17.4.3
 empty_files == 0.0.9