message: Remove patrikhuber/eigen.git submodule
  Will add the new official Eigen GitHub mirror
diff: [submodule "3rdparty/cereal"]
  path = 3rdparty/cereal
  url = https://github.com/USCiLab/cereal.git
  -[submodule "3rdparty/eigen"]
  - path = 3rdparty/eigen
  - url = https://github.com/patrikhuber/eigen.git
  [submodule "3rdparty/toml11"]
  path = 3rdparty/toml11
  url = https://github.com/ToruNiina/toml11.git
  