[xmlunit/xmlunit.net] dda76b: travis doesn't support "latest" for .NET Core SDK

[Stefan B. <no...@gi...>]

  Branch: refs/heads/netstandard-2.0
  Home:   https://github.com/xmlunit/xmlunit.net
  Commit: dda76b544770582d232fc66129036bfb08569f74
      https://github.com/xmlunit/xmlunit.net/commit/dda76b544770582d232fc66129036bfb08569f74
  Author: Stefan Bodewig <ste...@fr...>
  Date:   2019-04-04 (Thu, 04 Apr 2019)

  Changed paths:
    M .travis.yml

  Log Message:
  -----------
  travis doesn't support "latest" for .NET Core SDK