Modernise project relationship page (#9461)

Co-authored-by: Daniel Beck <1831569+daniel-beck@users.noreply.github.com>

core/src/main/java/jenkins/model/Jenkins.java

@@ -183,6 +183,7 @@ import hudson.triggers.Trigger;
 import hudson.triggers.TriggerDescriptor;
 import hudson.util.AdministrativeError;
 import hudson.util.ClockDifference;
+import hudson.util.ComboBoxModel;
 import hudson.util.CopyOnWriteList;
 import hudson.util.CopyOnWriteMap;
 import hudson.util.DaemonThreadFactory;
@@ -1908,6 +1909,11 @@ public class Jenkins extends AbstractCIBase implements DirectlyModifiableTopLeve
         return names;
     }
 
+    @Restricted(NoExternalUse.class)
+    public ComboBoxModel doFillJobNameItems() {
+        return new ComboBoxModel(getJobNames());
+    }
+
     @Override
     public List<Action> getViewActions() {
         return getActions();