Bump github.com/aws/aws-sdk-go-v2/service/ecrpublic from 1.21.2 to 1.21.6 in /tools/release/image-mirror #641

Job	Run time
validate-markdown	14s
get-test-cases	9s
create-test-ref	1s
changes	7s
build-windows	30m 1s
build	28m 13s
packaging-msi	1m 59s
packaging-rpm	49s
packaging-deb	26s
run-test-case (statsd_mock)	34s
run-test-case (otlp_metric_mock)	16s
run-test-case (otlp_mock)	25s
run-test-case (otlp_grpc_exporter_metric_mock)	18s
run-test-case (otlp_grpc_exporter_trace_mock)	29s
run-test-case (otlp_http_exporter_metric_mock)	20s
run-test-case (otlp_http_exporter_trace_mock)	24s
run-test-case (sapm_exporter_trace_mock)	18s
run-test-case (signalfx_exporter_metric_mock)	1m 15s
run-test-case (dynatrace_exporter_metric_mock)	20s
run-test-case (datadog_exporter_metric_mock)	24s
run-test-case (datadog_exporter_trace_mock)	32s
run-test-case (prometheus_mock)	18s
run-test-case (zipkin_mock)	38s
run-test-case (jaeger_mock)	17s
run-test-case (logzio_exporter_trace_mock)	33s
test-control-stript	15s
	1h 9m 35s

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