docs: remove downstream images and point to ubi9 (#71)

Author: hairmare

README.md

@@ -28,12 +28,7 @@ USER 1001
 
 ## Downstream Base Images
 
-We provide specialised downstream images for select use cases.
-
-* [RaBe Python Base Image Minimal](https://github.com/radiorabe/container-image-python-minimal)
-* [RaBe S2I Core Image Minimal](https://github.com/radiorabe/container-image-rabe-s2i-core-minimal)
-  * [RaBe S2I Base Image Minimal](https://github.com/radiorabe/container-image-rabe-s2i-base-minimal)
-    * [RaBe S2I Python Image Minimal](https://github.com/radiorabe/container-image-rabe-s2i-python-minimal)
+None anymore, see [UBI9](https://github.com/radiorabe/container-image-ubi9-minimal) for current base images.
 
 ## Advanced Usage