Update the version of submodule of google/mathfu. (#240)
Update the version of submodule of google/mathfu. (#240)

The new version now has the https as the its submodules' URL. Previous
mathfu's submodule is using http for submodule and kokoro doesn't
support it.
google/vulkan_test_applications,google/vulkan_test_applications,google/vulkan_test_applications,google/vulkan_test_applications