Update mixed-reality.md

[rafek]

"There aren't any devices today that can run experiences across the entire spectrum." sentence isn't that relevant anymore.

[prmerger-automator[bot]]

@rafek : Thanks for your contribution! The author(s) have been notified to review your proposed change.

[rafek]

With a new wave of color passthrough VR devices, that sentence should be rephrased or just removed to not to cause confusion.

[opbld33]

Learn Build status updates of commit 327c501:

:white_check_mark: Validation status: passed

File	Status	Preview URL	Details
mixed-reality-docs/mr-dev-docs/discover/mixed-reality.md	:white_check_mark:Succeeded

For more details, please refer to the build report.

Note: Broken links written as relative paths are included in the above build report. For broken links written as absolute paths or external URLs, see the broken link report.

For any questions, please:

• Try searching the learn.microsoft.com contributor guides
• Post your question in the Learn support channel