Fix typo where apostrophe was used in forming possessive of 'it' (#2024)

Signed-off-by: Joseph Goldstone <joseph.goldstone@mac.com>
Co-authored-by: Doug Walker <doug.walker@autodesk.com>

Author: JGoldstone

docs/concepts/overview/introduction.rst

@@ -17,8 +17,8 @@ high fidelity color imaging in modern computer graphics. This section introduces
 those concepts and general workflow practices. Additional information can be
 found in Jeremy Selan's Cinematic Color `document <http://cinematiccolor.org/>`_.
 
-While OCIO is a color management library, it's only knowledge of color science
-comes from it's execution of the transforms defined in the OCIO configuration
+While OCIO is a color management library, its only knowledge of color science
+comes from its execution of the transforms defined in the OCIO configuration
 file. These transforms are either defined by the end user in a custom OCIO
 config or inherited from the publicly available configs.