Silence future-compatibility warnings in 2.16

[huonw]

Running Pants 2.16 in this repository has various warnings, and it causes breakage in 2.17. This fixes those warnings, and now DYNAMIC_TAG=1 PANTS_VERSION=2.17.0rc2 pants tailor --check update-build-files --check fix lint test package :: works.

Warnings:

08:57:03.06 [WARN] DEPRECATED: The autoflake plugin has moved to `pants.backend.python.lint.autoflake` (and from the `fmt` goal to the `fix` goal).

...

08:57:07.98 [WARN] DEPRECATED: the 'outputs' field is scheduled to be removed in version 2.17.0.dev0.

Using the `outputs` field in the target src/docker/hello_world:hello_msg. To fix, use `output_files` and `output_directories` instead.

...

08:57:12.38 [WARN] DEPRECATED: Using `dependencies` to specify execution-time dependencies for `shell_command`  is scheduled to be removed in version 2.17.0.dev0.

To clear this warning, use the `output_dependencies` and `execution_dependencies`fields. Set `execution_dependencies=()` if you have no execution-time dependencies.

This was detected by public repos tests runs like https://github.com/pantsbuild/pants/actions/runs/5592922948/jobs/10226005348