message: remove antlr submodule
diff: [submodule "third_party/googletest"]
  path = third_party/googletest
  url = https://github.com/google/googletest.git
  -[submodule "third_party/antlr4"]
  - path = third_party/antlr4
  - url = https://github.com/alainmarcel/antlr4.git
  +
  