[PLATFORM-1734] switch to using dependency proxy

Dockerfile

-FROM bitnami/kubectl:1.25 AS kubectl
+FROM ${CI_DEPENDENCY_PROXY_GROUP_IMAGE_PREFIX}bitnami/kubectl:1.25 AS kubectl
 
-FROM amazon/aws-cli:2.11.20
+FROM ${CI_DEPENDENCY_PROXY_GROUP_IMAGE_PREFIX}amazon/aws-cli:2.11.20
 ENTRYPOINT []
 COPY --from=kubectl /opt/bitnami/kubectl/bin/kubectl /usr/local/bin/kubectl