Accept conda channels' ToS when building the upstream docker image. (#9661)

This PR should fix [the
error](https://github.com/pytorch/xla/actions/runs/18161391171/job/51692786522)
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.

Author: ysiraichi

.github/upstream/install_conda.sh

@@ -27,6 +27,10 @@ function install_and_setup_conda() {
   fi
   export CMAKE_PREFIX_PATH="$(dirname $(which conda))/../"
 
+  # Accept Conda channel ToS.
+  conda tos accept --override-channels --channel https://repo.anaconda.com/pkgs/main
+  conda tos accept --override-channels --channel https://repo.anaconda.com/pkgs/r
+
   conda update -y -n base conda
   conda install -y python=$PYTHON_VERSION