.NET 4.5.1 support dropped

Author: nblumhardt

src/Serilog.Settings.Configuration/Serilog.Settings.Configuration.csproj

@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <Description>Microsoft.Extensions.Configuration (appsettings.json) support for Serilog.</Description>
-    <VersionPrefix>3.5.0</VersionPrefix>
+    <VersionPrefix>4.0.0</VersionPrefix>
     <Authors>Serilog Contributors</Authors>
     <TargetFrameworks>netstandard2.0;net461</TargetFrameworks>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>