Bump the baseline to 2.504.3

This is required as an updated version of the workflow-support plugin
requires this version and tests will not pass unless it's required.

Author: mtughan

pom.xml

@@ -30,7 +30,7 @@
     <ban-junit4-imports.skip>false</ban-junit4-imports.skip>
     <!-- https://www.jenkins.io/doc/developer/plugin-development/choosing-jenkins-baseline/ -->
     <jenkins.baseline>2.504</jenkins.baseline>
-    <jenkins.version>${jenkins.baseline}.1</jenkins.version>
+    <jenkins.version>${jenkins.baseline}.3</jenkins.version>
   </properties>
 
   <dependencyManagement>