Fix missing escape in Powershell example

[Fax]

The example for the colorscheme command was missing the escape backtick in front of the command separator.

[opbld33]

Learn Build status updates of commit 285ffa1:

:white_check_mark: Validation status: passed

File	Status	Preview URL	Details
TerminalDocs/command-line-arguments.md	:white_check_mark:Succeeded	View

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[nguyen-dows]

Great catch @Fax! Thank you so much for finding this! :)