fix: use multi-arch manifest digest for ubi-minimal base image (#630)

## Summary
Fix multi-arch image builds `maas-controller` Konflux Dockerfile.

## Description
The `ubi9/ubi-minimal` base image SHA in
`maas-controller/Dockerfile.konflux` was pointing to an amd64-only
platform digest (`80f3902b...`), causing CI multi-arch builds to fail
for arm64, ppc64le, and s390x targets.

Replace the platform-specific digest with the manifest list digest
(`83006d53...`) which correctly resolves to the appropriate image for
all four target platforms (amd64, arm64, ppc64le, s390x).
Reference -
https://catalog.redhat.com/en/software/containers/ubi9/ubi-minimal/615bd9b4075b022acc111bf5#registry-tokens

## How it was tested
- Verified the new manifest list digest resolves to distinct
platform-specific images for all four architectures using `skopeo
inspect` and `podman pull --platform`.
- Successfully built the full container image locally for amd64, arm64,
ppc64le, and s390x

## Merge criteria:
<!--- This PR will be merged by any repository approver when it meets
all the points in the checklist -->
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- [x] The commits are squashed in a cohesive manner and have meaningful
messages.
- [x] Testing instructions have been added in the PR body (for PRs
involving changes that are not immediately obvious).
- [x] The developer has manually tested the changes and verified that
the changes work


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Chores**
  * Updated base runtime image to latest version

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Signed-off-by: Chetan Kulkarni <chkulkar@redhat.com>
Signed-off-by: Chaitanya Kulkarni <chkulkar@redhat.com>

Author: chaitanya1731

maas-controller/Dockerfile.konflux

@@ -17,7 +17,7 @@ COPY . .
 USER root
 RUN CGO_ENABLED=${CGO_ENABLED} GOEXPERIMENT=${GOEXPERIMENT} GOOS=${TARGETOS:-linux} GOARCH=${TARGETARCH:-amd64} go build -a -trimpath -ldflags="-s -w" -o manager ./cmd/manager
 
-FROM --platform=$TARGETPLATFORM registry.access.redhat.com/ubi9/ubi-minimal@sha256:80f3902b6dcb47005a90e14140eef9080ccc1bb22df70ee16b27d5891524edb2
+FROM --platform=$TARGETPLATFORM registry.access.redhat.com/ubi9/ubi-minimal@sha256:83006d535923fcf1345067873524a3980316f51794f01d8655be55d6e9387183
 
 WORKDIR /