Use `heroku/builder:24` in README usage instructions #920

Job	Run time
Rust Code Linting	35s
Integration Tests (buildpacks/gradle, builder:24, amd64)	5m 0s
Integration Tests (buildpacks/jvm, builder:24, amd64)	4m 15s
Unit Tests	58s
Integration Tests (buildpacks/maven, builder:24, amd64)	4m 10s
Integration Tests (buildpacks/sbt, builder:24, amd64)	6m 23s
Integration Tests (buildpacks/gradle, builder:24, arm64)	4m 40s
Integration Tests (buildpacks/jvm, builder:24, arm64)	2m 52s
Integration Tests (buildpacks/maven, builder:24, arm64)	4m 2s
Integration Tests (buildpacks/sbt, builder:24, arm64)	6m 0s
Integration Tests (buildpacks/gradle, builder:22, amd64)	4m 35s
Integration Tests (buildpacks/jvm, builder:22, amd64)	3m 18s
Integration Tests (buildpacks/jvm-function-invoker, builder:22, amd64)	3m 46s
Integration Tests (buildpacks/maven, builder:22, amd64)	5m 11s
Integration Tests (buildpacks/sbt, builder:22, amd64)	6m 15s
Integration Tests (buildpacks/gradle, builder:20, amd64)	4m 5s
Integration Tests (buildpacks/jvm, builder:20, amd64)	3m 6s
Integration Tests (buildpacks/maven, builder:20, amd64)	4m 33s
Integration Tests (buildpacks/sbt, builder:20, amd64)	6m 5s
	1h 19m 49s

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