Update rules/Proj0500.md

Co-authored-by: Laura Kramer <[email protected]>

Author: CptWesley

rules/Proj0500.md

@@ -19,7 +19,7 @@ When you use packages that are only (privately) shared within your company
 those packages are advised to explicitly define a license. You
 might need to contact your legal department to define a proper license.
 
-This rules can detect missing licenses in NuGet spec files, but can not be
+This rule can detect missing licenses in NuGet spec files, but can not be
 considered legal advice, nor is this documentation.
 
 ## See