Fix syntax issue in UNT0002.md

[RaSan147]

Fixes #378

Checklist

• I have read the Contribution Guide ;
• There is an approved issue describing the change when contributing a new analyzer or suppressor ;
• I have added tests that prove my fix is effective or that my feature works ;
• I have added necessary documentation (if appropriate) ;

Short description of what this resolves:

There was double double-quote in string for a 6 years old doc file that's been still being linked in Visual Studio.

Changes proposed in this pull request:

• make them single double-quote " in both end of the string

[sailro]

Thank you!