Bump uk.org.webcompere:system-stubs-jupiter from 2.1.7 to 2.1.8

Bumps [uk.org.webcompere:system-stubs-jupiter](https://github.com/webcompere/system-stubs) from 2.1.7 to 2.1.8.
- [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-2.1.7...system-stubs-parent-2.1.8)

---
updated-dependencies:
- dependency-name: uk.org.webcompere:system-stubs-jupiter
  dependency-version: 2.1.8
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

build.gradle

@@ -79,7 +79,7 @@ dependencies {
     testImplementation group: 'org.mockito', name: 'mockito-core', version: '5.16.1'
     testImplementation group: 'org.skyscreamer', name: 'jsonassert', version: '1.5.3'
     testImplementation group: 'org.jsoup', name: 'jsoup', version: '1.19.1'
-    testImplementation group: 'uk.org.webcompere', name: 'system-stubs-jupiter', version: '2.1.7'
+    testImplementation group: 'uk.org.webcompere', name: 'system-stubs-jupiter', version: '2.1.8'
 }
 
 test {