Bump jenkins-test-harness

Bumps [jenkins-test-harness](https://github.com/jenkinsci/jenkins-test-harness) from 1954.v2e3fd5465b_a_6 to 1971.v8a_5a_6cfd6e5d.
- [Release notes](https://github.com/jenkinsci/jenkins-test-harness/releases)
- [Changelog](https://github.com/jenkinsci/jenkins-test-harness/blob/master/docs/CHANGELOG-OLD.md)
- [Commits](https://github.com/jenkinsci/jenkins-test-harness/commits)

---
updated-dependencies:
- dependency-name: org.jenkins-ci.main:jenkins-test-harness
  dependency-type: direct:development
...

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

pom.xml

@@ -79,7 +79,7 @@
     <jacoco-maven-plugin.version>0.8.10</jacoco-maven-plugin.version>
     <jenkins.version>2.361</jenkins.version>
     <jenkins-bom.version>${jenkins.version}</jenkins-bom.version>
-    <jenkins-test-harness.version>1954.v2e3fd5465b_a_6</jenkins-test-harness.version>
+    <jenkins-test-harness.version>1971.v8a_5a_6cfd6e5d</jenkins-test-harness.version>
     <lifecycle-mapping.version>1.0.0</lifecycle-mapping.version>
     <localizer-maven-plugin.version>1.31</localizer-maven-plugin.version>
     <maven-antrun-plugin.version>3.1.0</maven-antrun-plugin.version>