Review.rst: Rename `Github` to `GitHub`
Review.rst: Rename `Github` to `GitHub`

This fixes typo and changes Github -> GitHub.

Fixes https://github.com/coala/coala/issues/5512

SanketDG/coala,coala-analyzer/coala,coala/coala,coala/coala,jayvdb/coala,coala/coala,coala-analyzer/coala,coala-analyzer/coala,jayvdb/coala,SanketDG/coala,SanketDG/coala,jayvdb/coala