Disallow unreleased packages from build requirements

[pllim]

One should not rely on unreleased packages to build user-facing notebooks. Ideally, any "official" notebooks that users supposedly can run on their own should only be from stable (released) packages.

jdat_notebooks/requirements.txt

Line 66 in 5f32e1a

webbpsf @ git+https://github.com/spacetelescope/webbpsf@bb8706e6ebf3f8dc842bd37830449182854c0b11

jdat_notebooks/requirements.txt

Line 69 in 5f32e1a

git+https://github.com/kammerje/fouriever

Also see:

• ci_validation broken by anand0xff/ImPlaneIA #121