Use multiline string in test

Java 17 feature that makes code more readable

Thanks to OpenRewrite

Author: MarkEWaite

src/test/java/hudson/tasks/JavadocArchiverTest.java

@@ -101,10 +101,12 @@ public void doNotKeepAll() throws Exception {
     public void keepAllInPipeline() throws Exception {
         WorkflowJob job = r.createProject(WorkflowJob.class);
         job.setDefinition(new CpsFlowDefinition(
-                "node {\n"
-                        + "  writeFile text: 'generated by #'+env.BUILD_NUMBER, file: 'doc/index.html'\n"
-                        + "  javadoc javadocDir: 'doc', keepAll: true\n"
-                        + "}",
+                """
+                node {
+                  writeFile text: 'generated by #'+env.BUILD_NUMBER, file: 'doc/index.html'
+                  javadoc javadocDir: 'doc', keepAll: true
+                }
+                """,
                 true));
 
         WorkflowRun b1 = r.buildAndAssertSuccess(job);
@@ -119,10 +121,12 @@ public void keepAllInPipeline() throws Exception {
     public void doNotKeepAllInPipeline() throws Exception {
         WorkflowJob job = r.createProject(WorkflowJob.class);
         job.setDefinition(new CpsFlowDefinition(
-                "node {\n"
-                        + "  writeFile text: 'generated by #'+env.BUILD_NUMBER, file: 'doc/index.html'\n"
-                        + "  javadoc javadocDir: 'doc', keepAll: false\n"
-                        + "}",
+                """
+                node {
+                  writeFile text: 'generated by #'+env.BUILD_NUMBER, file: 'doc/index.html'
+                  javadoc javadocDir: 'doc', keepAll: false
+                }
+                """,
                 true));
 
         WorkflowRun b1 = r.buildAndAssertSuccess(job);