Revert "migrate the base images to the ubi9"

This reverts commit 761e22f.
Because of the FEDRAMP requirement we need to migrate back to the ubi8.

Dockerfile

@@ -2,7 +2,7 @@
 ############################
 # STEP 1 build executable binary
 ############################
-FROM registry.access.redhat.com/ubi9/go-toolset:latest AS builder
+FROM registry.access.redhat.com/ubi8/go-toolset:latest AS builder
 WORKDIR $GOPATH/src/mypackage/myapp/
 COPY . .
 # Fetch dependencies.
@@ -14,7 +14,7 @@ RUN CGO_ENABLED=0 go build -o /go/bin/uhc-auth-proxy
 ############################
 # STEP 2 build a small image
 ############################
-FROM registry.access.redhat.com/ubi9/ubi-minimal:latest
+FROM registry.access.redhat.com/ubi8/ubi-minimal:latest
 # Copy our static executable.
 COPY --from=builder /go/bin/uhc-auth-proxy /go/bin/uhc-auth-proxy
 # Default port