Update README badge from slack to forum #12302

Job	Run time
Checks and variables	1m 12s
NJS Unit Tests	11s
Unit Tests	49s
Build Binary	26s
Build Plus images / build	1m 38s
Build OSS images (nginx, linux/arm64, linux/amd64) / build	1m 25s
Build OSS images (ngf, linux/arm64, linux/amd64) / build	1m 12s
Helm Tests	0s
Conformance tests (nginx, v1.32.3, false) / Run Tests	6m 27s
Conformance tests (nginx, v1.32.3, true) / Run Tests	6m 28s
Conformance tests (nginx, v1.25.16, false) / Run Tests	7m 8s
Conformance tests (nginx, v1.25.16, true) / Run Tests	6m 34s
Conformance tests (plus, v1.25.16, false) / Run Tests	0s
Conformance tests (plus, v1.25.16, true) / Run Tests	0s
Conformance tests (plus, v1.32.3, false) / Run Tests	0s
Conformance tests (plus, v1.32.3, true) / Run Tests	0s
Functional tests (nginx, v1.25.16) / Run Tests	14m 9s
Functional tests (nginx, v1.32.3) / Run Tests	12m 52s
Functional tests (plus, v1.25.16) / Run Tests	0s
Functional tests (plus, v1.32.3) / Run Tests	0s
Package and Publish Helm Chart	0s
	1h 0m 31s

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