Bump uk.org.webcompere:system-stubs-jupiter from 2.1.5 to 2.1.6

Bumps [uk.org.webcompere:system-stubs-jupiter](https://github.com/webcompere/system-stubs) from 2.1.5 to 2.1.6.
- [Release notes](https://github.com/webcompere/system-stubs/releases)
- [Changelog](https://github.com/webcompere/system-stubs/blob/main/History.md)
- [Commits](webcompere/system-stubs@system-stubs-parent-2.1.5...system-stubs-parent-2.1.6)

---
updated-dependencies:
- dependency-name: uk.org.webcompere:system-stubs-jupiter
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

build.gradle

@@ -76,7 +76,7 @@ dependencies {
   testImplementation group: 'org.jsoup', name: 'jsoup', version: '1.17.2'
   testImplementation project.deps.gocdPluginApi
   testImplementation group: 'org.skyscreamer', name: 'jsonassert', version: '1.5.1'
-  testImplementation 'uk.org.webcompere:system-stubs-jupiter:2.1.5'
+  testImplementation 'uk.org.webcompere:system-stubs-jupiter:2.1.6'
 }