Bump the onbuild images too

They missed the 9.2.8.0 update.

library/jruby

@@ -11,7 +11,7 @@ Tags: 9-jdk, 9.2-jdk, 9.2.9-jdk, 9.2.9.0-jdk
 Architectures: amd64
 Directory: 9000/jdk
 
-Tags: 9-onbuild, 9.2-onbuild, 9.2.7-onbuild, 9.2.7.0-onbuild
+Tags: 9-onbuild, 9.2-onbuild, 9.2.9-onbuild, 9.2.9.0-onbuild
 Architectures: amd64
 Directory: 9000/onbuild