bump framework to re-enable Actions tests for non-Windows environments (#2071)

build/Context.cs

@@ -42,7 +42,7 @@ public class Context : FrostingContext
 
         if (!this.IsRunningOnWindows())
         {
-            var testFramework = "netcoreapp2.0";
+            var testFramework = "netcoreapp2.1";
 
             this.Information($"Running tests against {testFramework} only as we're not on Windows.");
             settings.Framework = testFramework;
@@ -55,4 +55,4 @@ public class Context : FrostingContext
         : base(context)
     {
     }
-}
+}