docs: Fix a few typos

[timgates42]

There are small typos in:

• green/loader.py
• green/output.py
• green/result.py

Fixes:

• Should read overridden rather than overriden.
• Should read hierarchies rather than heirarchies.
• Should read expected rather than expeced.
• Should read additional rather than additonal.

Semi-automated pull request generated by https://github.com/timgates42/meticulous/blob/master/docs/NOTE.md

[coveralls]

Coverage remained the same at 100.0% when pulling ad2c8ac4fde1f690cd7e4bcb5132d4dfa751c7d3 on timgates42:bugfix_typos into ddfec93f85bef3772dfa6b13a08e9176c5c8c961 on CleanCut:main.