Chore: Change license from GPLv3 to Apache-v2

[adrien-berchet]

Description

OBP workflows require more permissive licenses so let's change it here.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.86%. Comparing base (ad427ad) to head (8613050).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #106      +/-   ##
==========================================
- Coverage   97.86%   97.86%   -0.01%     
==========================================
  Files          39       39              
  Lines        2201     2200       -1     
  Branches      383      382       -1     
==========================================
- Hits         2154     2153       -1     
  Misses         29       29              
  Partials       18       18              

Flag	Coverage Δ
pytest	97.86% <100.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
neurots/__init__.py	100.00% <ø> (ø)
neurots/astrocyte/context.py	76.19% <ø> (ø)
neurots/astrocyte/grower.py	93.10% <ø> (ø)
neurots/astrocyte/point_cloud.py	98.36% <ø> (ø)
neurots/astrocyte/section.py	80.24% <ø> (ø)
neurots/astrocyte/space_colonization.py	94.32% <ø> (ø)
neurots/astrocyte/tmd_utils.py	82.35% <ø> (ø)
neurots/astrocyte/tree.py	100.00% <ø> (ø)
neurots/basic.py	100.00% <ø> (ø)
neurots/extract_input/__init__.py	100.00% <ø> (ø)
... and 29 more