CleanUp: remove two temporary features in gitOrigin
CleanUp: remove two temporary features in gitOrigin

These two features (cache prefix and submodule fetch all) are stable now. It is time to remove them.

PiperOrigin-RevId: 344799260
Change-Id: I5707ad8144942d3666671e1ab63d14618b047902

google/copybara,google/copybara,google/copybara