bump Newtonsoft.Json to v12.0.3

Author: jetersen

src/GitLabApiClient/GitLabApiClient.csproj

@@ -20,7 +20,7 @@
   <ItemGroup>
     <PackageReference Include="GitVersionTask" Version="5.1.2" PrivateAssets="All" />
     <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.0.0-beta2-19367-01" PrivateAssets="All" />
-    <PackageReference Include="Newtonsoft.Json" Version="10.0.3" />
+    <PackageReference Include="Newtonsoft.Json" Version="12.0.3" />
   </ItemGroup>
 
   <ItemGroup Condition="'$(TargetFramework)' == 'net452'">