Bumping to 2.121.1 because required by workflow-step-api baseline

```
Caused by: java.io.IOException: Pipeline: Step API v2.19 failed to load.
 - You must update Jenkins from v2.107.3 to v2.121.1 or later to run this plugin.
        at hudson.PluginWrapper.resolvePluginDependencies(PluginWrapper.java:655)
```

Author: batmat

pom.xml

@@ -26,7 +26,7 @@
   <properties>
     <revision>4.0.0-beta8</revision>
     <changelist>-SNAPSHOT</changelist>
-    <jenkins.version>2.107.3</jenkins.version>
+    <jenkins.version>2.121.1</jenkins.version>
     <java.level>8</java.level>
     <no-test-jar>false</no-test-jar>
     <concurrency>1C</concurrency>