chore: standardize format of BUILD overrides

[cognifloyd]

Quick/minor reformat of some BUILD files.

I like to use dict() under overrides so that syntax highlighting looks similar to a regular target.

So, use this

python_sources(
    overrides={
        "foobar.py": dict(
            dependencies=[...],
        ),
    },
)

instead of this

python_sources(
    overrides={
        "foobar.py": {
            "dependencies": [...],
        },
    },
)