fix possessive typo

[lancehilliard]

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue).

• [ ] New feature (non-breaking change which adds functionality).

• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected).

• [ ] Performance improvement

• [ ] Refactoring (so no functional change)

• [x] Other (docs, build config, etc)

• [ ] I've added tests for my code. (most of the time mandatory)

• [ ] I have added an entry to the changelog. (mandatory)

• [x] My change requires a change to the documentation.

• [x] I have updated the documentation accordingly.