Fix Read the Docs configuration

[Mandrenkov]

Context:

Currently, the Read the Docs builds are failing due to the following error:

Error
Problem in your project's configuration. Invalid configuration option "build.os": os not found

Description of the Change:

• Fixed the Read the Docs configuration file based on the Xanadu Sphinx Theme.

Benefits:

• The Read the Docs builds are passing.

Possible Drawbacks:

None.

Related GitHub Issues:

None.