Only return exit code != 0 if fatal error occurs.

- We were returning a 1 exit code in the case that we could not resolve a `TagHelper` assembly. This error isn't fatal and is logged/reported via the error sink.

Author: N. Taylor Mullen

src/dotnet-razor-tooling/Internal/ResolveTagHelpersCommand.cs

@@ -77,7 +77,7 @@ internal static void Register(CommandLineApplication app)
 
                     Reporter.Output.WriteLine(serializedResult);
 
-                    return errorSink.Errors.Any() ? 1 : 0;
+                    return 0;
                 });
             });
         }