Update rules/Proj0504.md

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

Author: Corniel

rules/Proj0504.md

@@ -25,7 +25,7 @@ license is different than the license approved one.
     <PackageReference Include="SonarAnalyzer.CSharp" Version="10.6.0.109712" />
   </ItemGroup>
 
-  <ItemGroup Label="Aproved licenses">
+  <ItemGroup Label="Approved licenses">
     <ThirdPartyLicense Include="SonarAnalyzer.CSharp" Hash="ADifferentHash" />
   </ItemGroup>