chore: update NuGet packages

Author: jcdcdev

src/jcdcdev.Umbraco.ReadingTime.TestSite/jcdcdev.Umbraco.ReadingTime.TestSite.csproj

@@ -6,8 +6,8 @@
     </PropertyGroup>
 
     <ItemGroup>
-        <PackageReference Include="Umbraco.Cms" Version="[15.0.0,16.0.0)" />
-        <PackageReference Include="uSync" Version="15.0.1"/>
+        <PackageReference Include="Umbraco.Cms" Version="15.3.1" />
+        <PackageReference Include="uSync" Version="15.1.6"/>
     </ItemGroup>
 
     <ItemGroup>