Remove '--quiet' option from git commands in /configure.

Should we display information about `git submodule` when `configure` ?

When I called `configure` after cloning servo repository, it resolved and initialized git sub modules. However, the first `git submodule` after clone the repository needs long times for initializing sub repository (e.g. skia, rust) and it doesn't display any progress about submodules. At this time, we cannot know that `configure` works correctly, or has some error if we uses `--quiet` option.

I think we shouldn't use `--quiet` option.