Accept conda channels' ToS when building the upstream docker image.

[ysiraichi]

This PR should fix the error we've been getting when trying to build the upstream image. It simply adds to the install_conda.sh script what conda suggests us to do:

#23 12.71 CondaToSNonInteractiveError: Terms of Service have not been accepted for the following channels. Please accept or remove them before proceeding:
#23 12.71     - https://repo.anaconda.com/pkgs/main
#23 12.71     - https://repo.anaconda.com/pkgs/r
#23 12.71 
#23 12.71 To accept these channels' Terms of Service, run the following commands:
#23 12.71     conda tos accept --override-channels --channel https://repo.anaconda.com/pkgs/main
#23 12.71     conda tos accept --override-channels --channel https://repo.anaconda.com/pkgs/r
#23 12.71 
#23 12.71 For information on safely removing channels from your conda configuration,
#23 12.71 please see the official documentation:
#23 12.71 
#23 12.71     https://www.anaconda.com/docs/tools/working-with-conda/channels