RenovateBot: Update node Docker tag to v20

This MR contains the following updates:

Package	Type	Update	Change
node	image	major	18 -> 20
node	final	major	18 -> 20

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.gitlab-ci.yml

@@ -47,7 +47,7 @@ e2e_test:
 
 # Build the application
 .build_frontend_template: &build_frontend-template
-  image: node:18
+  image: node:20
   stage: build
   cache:
     key: ${CI_COMMIT_REF_SLUG}