Fix small typo: `instal` ➝ `install`

[mrienstra]

Very minor change.

[learn-build-service-prod[bot]]

Learn Build status updates of commit 59fe051:

:white_check_mark: Validation status: passed

File	Status	Preview URL	Details
WSL/basic-commands.md	:white_check_mark:Succeeded	View

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[mattwojo]

Thank you for catching this @mrienstra!