fix dotnet build for linux

Author: TorstenDittmann

templates/dotnet/src/Appwrite/Appwrite.csproj.twig

@@ -1,7 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <TargetFrameworks>netcoreapp3.1;net461;netstandard2.0;</TargetFrameworks>
-    <TargetFrameworks Condition=" '$(OS)' != 'Windows_NT' ">netstandard2.0</TargetFrameworks>
     <PackageId>{{spec.title}}</PackageId>
     <Version>{{sdk.version}}</Version>
     <Authors>{{spec.contactName}}</Authors>