Merge pull request #718 from danielcweber/NoExplicitLangVersionDowngrade

Don't downgrade the language version.

Rx.NET/Source/src/Microsoft.Reactive.Testing/Microsoft.Reactive.Testing.csproj

@@ -7,7 +7,6 @@
     <DefineConstants>$(DefineConstants);PLATFORM_DOTNET;XUNIT_VISIBILITY_INTERNAL</DefineConstants>        
     <PackageTags>Rx;Reactive;Extensions;Observable;LINQ;Events</PackageTags>    
     <Description>Reactive Extensions (Rx) for .NET - Testing Library</Description>
-    <LangVersion>7.1</LangVersion>
   </PropertyGroup>
 
   <ItemGroup>

Rx.NET/Source/tests/Tests.System.Reactive/Tests.System.Reactive.csproj

@@ -2,7 +2,6 @@
   <PropertyGroup>
     <TargetFrameworks>net46;netcoreapp2.0</TargetFrameworks>
     <NoWarn>$(NoWarn);CS0618</NoWarn>
-    <LangVersion>7.1</LangVersion>
   </PropertyGroup>
   
   <ItemGroup>