Remove python_new_version feature flag and irrelevant code #15401

Job	Run time
approval	10s
push-updater-images (bundler, bundler)	29s
push-updater-images (cargo, cargo)	1m 12s
push-updater-images (composer, composer)	1m 58s
push-updater-images (docker, docker)	32s
push-updater-images (elm, elm)	32s
push-updater-images (git_submodules, gitsubmodule)	25s
push-updater-images (github_actions, github-actions)	38s
push-updater-images (go_modules, gomod)	1m 55s
push-updater-images (gradle, gradle)	32s
push-updater-images (hex, mix)	1m 46s
push-updater-images (maven, maven)	28s
push-updater-images (npm_and_yarn, npm)	1m 7s
push-updater-images (nuget, nuget)	2m 44s
push-updater-images (pub, pub)	1m 31s
push-updater-images (python, pip)	1m 53s
push-updater-images (swift, swift)	4m 36s
push-updater-images (devcontainers, devcontainers)	48s
push-updater-images (terraform, terraform)	37s
	23m 53s

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