Pin base image to 9.6 tag

The base image for latest tag got update to 9.7 where fips test
started to fail. This pins it for now to the 9.6 tag

Signed-off-by: Martin Schuppert <[email protected]>

Author: stuggi

Dockerfile

@@ -1,5 +1,5 @@
 ARG GOLANG_BUILDER=registry.access.redhat.com/ubi9/go-toolset:1.24
-ARG OPERATOR_BASE_IMAGE=registry.access.redhat.com/ubi9/ubi-minimal:latest
+ARG OPERATOR_BASE_IMAGE=registry.access.redhat.com/ubi9/ubi-minimal:9.6
 # Build the manager binary
 FROM $GOLANG_BUILDER AS builder