Update Add-LabDiskDefinition.md

[KloudGeek]

Corrected typographical errors.

Description

Please describe your changes in detail, unless the title is already descriptive enough.

• - I have tested my changes.
• - I have updated CHANGELOG.md and added my change to the Unreleased section
• - The PR has a meaningful title.
• - I updated my fork/branch and have integrated all changes from AutomatedLab/develop before creating the PR.

Type of change

• Bug fix
• New functionality
• Breaking change
• Documentation

How was the change tested?

[raandree]

Thanks.