docs: Mark NiFi 2.4.0 as supported

Author: NickLarsenNZ

docs/modules/nifi/partials/supported-versions.adoc

@@ -2,7 +2,7 @@
 // This is a separate file, since it is used by both the direct NiFi-Operator documentation, and the overarching
 // Stackable Platform documentation.
 
-* 2.4.0 (experimental) - Please note that you need to upgrade to at least 1.27.x before upgrading to 2.x.x!
+* 2.4.0 (Please note that you need to upgrade to at least 1.27.x before upgrading to 2.x.x!)
 * 1.28.1
 * 1.27.0 (LTS)