Clear getting started section #19924

Job	Run time
build_cmake (alpine:3.23, false, false)	58s
build_make (ubuntu:25.10)	4m 22s
build_cmake (ubuntu:25.10, true, true)	4m 7s
build_make (ubuntu:24.04)	3m 52s
build_make (alpine:3.23)	5m 46s
build_cmake (ubuntu:24.04, true, true)	4m 25s
	23m 30s

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