fix: replace third-party curl image with UBI-based image for disconnected support (#706)

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## Description
Replace curlimages/curl with registry.redhat.io/ubi9/ubi-minimal:9.7 in
the cleanup CronJob. Third-party images are not mirrored in
disconnected/air-gapped RHOAI environments. UBI minimal includes curl
and is available in the RHOAI mirror catalog.

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

* **Chores**
  * Updated the container base image used for the API cleanup process.

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

Signed-off-by: Wen Liang <liangwen12year@gmail.com>

Author: liangwen12year

deployment/base/maas-api/core/cronjob-cleanup.yaml

@@ -22,7 +22,7 @@ spec:
             runAsNonRoot: true
           containers:
           - name: cleanup
-            image: curlimages/curl:8.18.0
+            image: registry.redhat.io/ubi9/ubi-minimal:9.7
             command:
             - /bin/sh
             - -c