Modernize to Jenkins 2.440.3 (#992)

Co-authored-by: Moderne <[email protected]>

pom.xml

@@ -19,7 +19,7 @@
     <properties>
         <changelist>999999-SNAPSHOT</changelist>
         <gitHubRepo>jenkinsci/slack-plugin</gitHubRepo>
-        <jenkins.version>2.426.3</jenkins.version>
+        <jenkins.version>2.440.3</jenkins.version>
         <hpi.compatibleSinceVersion>2.32</hpi.compatibleSinceVersion>
         <checkstyle.failsOnError>true</checkstyle.failsOnError>
         <checkstyle.failOnViolation>true</checkstyle.failOnViolation>
@@ -50,8 +50,8 @@
         <dependencies>
             <dependency>
                 <groupId>io.jenkins.tools.bom</groupId>
-                <artifactId>bom-2.426.x</artifactId>
-                <version>3208.vb_21177d4b_cd9</version>
+                <artifactId>bom-2.440.x</artifactId>
+                <version>3234.v5ca_5154341ef</version>
                 <scope>import</scope>
                 <type>pom</type>
             </dependency>