Bump golang.org/x/net from 0.21.0 to 0.23.0 in /testbed #4001

Job	Run time
changes	6s
create-test-ref	3s
get-test-cases	3s
validate-markdown	10s
build	21m 34s
build-windows	22m 19s
packaging-msi	1m 27s
packaging-rpm	42s
packaging-deb	25s
run-test-case (statsd_mock)	18s
run-test-case (otlp_metric_mock)	22s
run-test-case (otlp_mock)	18s
run-test-case (otlp_grpc_exporter_metric_mock)	21s
run-test-case (otlp_grpc_exporter_trace_mock)	23s
run-test-case (otlp_http_exporter_metric_mock)	20s
run-test-case (otlp_http_exporter_trace_mock)	21s
run-test-case (sapm_exporter_trace_mock)	16s
run-test-case (signalfx_exporter_metric_mock)	21s
run-test-case (datadog_exporter_metric_mock)	22s
run-test-case (datadog_exporter_trace_mock)	23s
run-test-case (prometheus_mock)	17s
run-test-case (zipkin_mock)	19s
run-test-case (jaeger_mock)	16s
run-test-case (logzio_exporter_trace_mock)	22s
test-control-stript	10s
	51m 58s

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