remove nca3.0 so CI server can build it

Dapper.Tests/Dapper.Tests.csproj

@@ -6,7 +6,7 @@
     <GenerateDocumentationFile>false</GenerateDocumentationFile>
     <AutoGenerateBindingRedirects>true</AutoGenerateBindingRedirects>
     <GenerateBindingRedirectsOutputType>true</GenerateBindingRedirectsOutputType>
-    <TargetFrameworks>netcoreapp2.1;net462;net472;netcoreapp3.0</TargetFrameworks>
+    <TargetFrameworks>netcoreapp2.1;net462;net472</TargetFrameworks>
     <TreatWarningsAsErrors>false</TreatWarningsAsErrors>
   </PropertyGroup>
 

Dapper.sln

@@ -9,6 +9,7 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution
 		appveyor.yml = appveyor.yml
 		build.ps1 = build.ps1
 		Directory.build.props = Directory.build.props
+		global.json = global.json
 		docs\index.md = docs\index.md
 		License.txt = License.txt
 		nuget.config = nuget.config

global.json

 
 {
   "sdk": {
-    "version": "3.0-preview8"
+    "version": "2.2.203"
   }
 }
\ No newline at end of file