Update NLog to latest version, instead of BETA

From: https://github.com/stratisproject/BlockExplorer/blob/master/IndexStore/Stratis.IndexStoreD/Stratis.IndexStoreD.csproj

```
<PackageReference Include="NLog" Version="5.0.0-beta09" />
<PackageReference Include="NLog.Extensions.Logging" Version="1.0.0-rtm-beta5" /> 
```

NLog 4.5 (And newer) supports NetCore: https://www.nuget.org/packages/NLog/