docs: add missing popd to post-extract example
docs: add missing popd to post-extract example

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dokku/dokku,progrium/dokku,jimjag/dokku,jimjag/dokku,dokku/dokku,jimjag/dokku,progrium/dokku,claytonbrown/dokku,jimjag/dokku,claytonbrown/dokku,progrium/dokku,jimjag/dokku,dokku/dokku,dokku/dokku,progrium/dokku,dokku/dokku,claytonbrown/dokku,jimjag/dokku,dokku/dokku,claytonbrown/dokku,claytonbrown/dokku,progrium/dokku,dokku/dokku,dokku/dokku,progrium/dokku,progrium/dokku,jimjag/dokku,claytonbrown/dokku,jimjag/dokku,progrium/dokku,claytonbrown/dokku,claytonbrown/dokku