delete old readme.md file #2061

Job	Run time
build (macos-13, tests/github_actions_test_macos_1a.jsonc, tests/github_actions_test_macos_1b.jso...	11m 18s
build (ubuntu-latest, tests/github_actions_test_ubuntu_1a.jsonc, tests/github_actions_test_ubuntu...	5m 51s
	17m 9s

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