environment.yml uses conda channel 'default' instead of 'defaults'; trailing space in _toc.yml

Mở environment.yml và lectures/_toc.yml, sau đó so sánh cách viết channel với dạng đã được sửa và đang được dùng trong bản zh-cn. Đổi default thành defaults và xóa khoảng trắng ở cuối sau workspace; chạy jb build để xác nhận rằng cấu hình vẫn được phân giải và build thành công, không có lỗi.

Two small defects in the build configuration, both found while porting this repo's scaffold into the new lecture-python-programming.ml edition (QuantEcon/lecture-python-programming.ml#6). Neither breaks the build today; the first is a latent failure worth getting ahead of.

1. environment.yml names the conda channel default, not defaults

default is not a conda channel. Conda adds it as a literal channel name and then resolves the packages from defaults, which it still adds implicitly — and warns about doing so:

Adding channel 'default'
[command]/home/runner/miniconda3/condabin/conda config --add channels default
##[warning]The 'defaults' channel might have been added implicitly. If this is intentional, add 'defaults' to the 'channels' list. Otherwise, consider setting 'conda-remove-defaults' to 'true'.

So the environment resolves by accident. Conda is deprecating the implicit-defaults behaviour, and when it goes the build fails to resolve anything.

This affects three editions — this repo, lecture-python-programming.fr and lecture-python-programming.fa — all of which carry - default. lecture-python-programming.zh-cn already has - defaults and is unaffected, so the corrected form is already proven in the fleet.

The fix is one word in environment.yml.

2. lectures/_toc.yml line 39 has a trailing space

The entry reads - file: workspace rather than - file: workspace. This is harmless in practice — YAML strips trailing whitespace from plain scalars, so both jb build and any tooling reading the file see workspace — but it propagates verbatim into every translation edition, since action-translation copies _toc.yml from source as-is. It surfaced as a review comment on the downstream PR, where fixing it locally would only have created drift against this repo.

Worth correcting here so it stops being re-copied.