Further version ignore in dependabot (#539)

Co-authored-by: Chris Kittl <[email protected]>

Author: sebastian-peter

.github/dependabot.yml

@@ -21,3 +21,4 @@ updates:
         - "2.1-groovy-2.5-SNAPSHOT"
         - "2.2-groovy-4.0-SNAPSHOT"
         - "2.2-groovy-3.0-SNAPSHOT"
+        - "2.2-groovy-2.5-SNAPSHOT"