Update "assimp" package

[NukeBird]

https://github.com/assimp/assimp/releases/tag/v5.0.0 (2d2889f)

I think it's very important update:

Implemented basic PBR materials into assimp.
This adds the following texture types:
BASE_COLOR
NORMAL_CAMERA
EMISSION_COLOR
METALNESS
DIFFUSE_ROUGHNESS

Add support for importing GLTF2 animations.

[NukeBird]

actually I noticed just now that assimp uses hunter (but the ruslo ones, old version)
so update should be pretty straightforward

[rbsheth]

@NukeBird Want to try your hand at updating the package? Like you said, it should be very straightforward since I added Hunter support directly there. If you do, make sure to test your updated branch with CI (https://docs.hunter.sh/en/latest/creating-new/update.html#testing).