Checklist

[X] The title and commit message(s) are descriptive.
[X] Small commits made to fix your PR have been squashed to avoid history pollution.
[ ] Tests have been added for new features or bug fixes.
[ ] API of new functions and classes are documented.

Description

Fixes typo in documentation entry for xt::right_shift that incorrectly describes it as if referring to xt::left_shift.