Update Node.js from 18.x to 20.x (#8571)

.github/renovate.json

@@ -16,7 +16,7 @@
     },
     {
       "matchPackageNames": ["node"],
-      "allowedVersions": "/18.[0-9]+.[0-9]+(.[0-9]+)?$/"
+      "allowedVersions": "/20.[0-9]+.[0-9]+(.[0-9]+)?$/"
     }
   ],
   "regexManagers": [

CONTRIBUTING.md

@@ -14,7 +14,7 @@ This page provides information about contributing code to the Jenkins core codeb
    - Apache Maven 3.8.1 or above. You can [download Maven here](https://maven.apache.org/download.cgi).
      In the Jenkins project we usually use the most recent Maven release.
    - Any IDE which supports importing Maven projects.
-   - Install [Node.js 18.x](https://nodejs.org/en/). **Note:** only needed to work on the frontend assets found in the `war` module.
+   - Install [Node.js 20.x](https://nodejs.org/en/). **Note:** only needed to work on the frontend assets found in the `war` module.
      - Frontend tasks are run using [yarn](https://yarnpkg.com/). Run `npm install -g yarn` to install it.
 4. Set up your development environment as described in [Preparing for Plugin Development](https://www.jenkins.io/doc/developer/tutorial/prepare/)
 

war/pom.xml

@@ -46,7 +46,7 @@ THE SOFTWARE.
     <host>localhost</host>
     <!-- HTTP listener port -->
     <port>8080</port>
-    <node.version>18.18.0</node.version>
+    <node.version>20.8.0</node.version>
     <!-- frontend-maven-plugin will install this Yarn version as bootstrap, then hand over control to Yarn Berry. -->
     <yarn.version>1.22.19</yarn.version>
     <!-- maven-antrun-plugin will download this Yarn version. -->