Stop installing .NET Core 1.x, 2.0 on Azure Pipelines

azure-pipelines/build.yml

@@ -4,16 +4,6 @@ steps:
   inputs:
     packageType: sdk
     version: 2.2.300
-- task: UseDotNet@2
-  displayName: Install .NET Core runtime 1.0.x
-  inputs:
-    packageType: runtime
-    version: 1.0.x
-- task: UseDotNet@2
-  displayName: Install .NET Core runtime 2.0.x
-  inputs:
-    packageType: runtime
-    version: 2.0.x
 - task: UseDotNet@2
   displayName: Install .NET Core runtime 2.1.x
   inputs: