Update module github.com/prometheus/client_golang to v1.20.1 - abandoned #323

Job	Run time
Checks and variables	1m 31s
Unit Tests	3m 9s
NJS Unit Tests	9s
Build Binary	41s
Build Plus images / build	51s
Build OSS images (nginx, linux/arm64, linux/amd64) / build	48s
Build OSS images (ngf, linux/arm64, linux/amd64) / build	1m 21s
Helm Tests	0s
Conformance tests (nginx, v1.25.16, false) / Run Tests	1s
Conformance tests (nginx, v1.25.16, true) / Run Tests	1s
Conformance tests (nginx, v1.31.0, false) / Run Tests	1s
Conformance tests (nginx, v1.31.0, true) / Run Tests	1s
Conformance tests (plus, v1.25.16, false) / Run Tests	1s
Conformance tests (plus, v1.31.0, false) / Run Tests	1s
Conformance tests (plus, v1.25.16, true) / Run Tests	1s
Conformance tests (plus, v1.31.0, true) / Run Tests	1s
Functional tests (nginx, v1.25.16) / Run Tests	1s
Functional tests (nginx, v1.31.0) / Run Tests	1s
Functional tests (plus, v1.25.16) / Run Tests	1s
Functional tests (plus, v1.31.0) / Run Tests	1s
Package and Publish Helm Chart	0s
	8m 42s

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