Bump go.opentelemetry.io/collector/config/confignet from 0.80.0 to 1.21.0 in /testbed #15926

Job	Run time
govulncheck (receiver-0)	1m 50s
govulncheck (receiver-1)	1m 50s
setup-environment	0s
govulncheck (processor)	1m 51s
govulncheck (exporter)	1m 58s
govulncheck (extension)	1m 53s
govulncheck (connector)	1m 58s
govulncheck (internal)	1m 48s
govulncheck (pkg)	1m 49s
check-collector-module-version	0s
build-examples	0s
check-codeowners	0s
correctness-metrics	0s
checks	0s
integration-tests	0s
correctness-traces	0s
lint-matrix	0s
unittest-matrix	0s
lint	0s
unittest	0s
coverage	0s
cross-compile	0s
build-package	0s
windows-msi	0s
publish-check	0s
publish-dev	0s
publish-stable	0s
rotate-milestone	0s
	14m 57s

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