New-xDscResource: Change Dsc Module Validate Set Quotes to Singles

[X-Guardian]

Pull Request (PR) description

This PR changes the quotes used around validate set values to be single quotes instead of double quotes to conform to Dsc Resource Style Guidelines

This Pull Request (PR) fixes the following issues

None

Task list

• [ ] Added an entry under the Unreleased section of the change log in the README.md. Entry should say what was changed, and how that affects users (if applicable).
• [ ] Documentation added/updated in README.md.
• [ ] Comment-based help added/updated for all new/changed functions.
• [ ] Localization strings added/updated in all localization files as appropriate.
• [x] Unit tests added/updated.
• [x] New/changed code adheres to DSC Resource Style Guidelines and Best Practices.

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This change is 

[codecov-io]

Codecov Report

Merging #83 into dev will increase coverage by 1.11%. The diff coverage is 75%.

@@            Coverage Diff             @@
##              dev      #83      +/-   ##
==========================================
+ Coverage   61.26%   62.38%   +1.11%     
==========================================
  Files           1        1              
  Lines         994      997       +3     
  Branches        3        3              
==========================================
+ Hits          609      622      +13     
+ Misses        382      372      -10     
  Partials        3        3

Impacted Files	Coverage Δ
xDSCResourceDesigner.psm1	62.38% <75%> (+1.11%)	:arrow_up:

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