setup-binary-builds: explicitly install pip in pkg-helpers conda env

Conda 25.x (pulled in by miniconda "latest") no longer installs pip by
default when only python=X.Y is requested. This breaks
pytorch_pkg_helpers setup with "No module named pip" when running
`python -m pip install ...` in the freshly-created env.

Add `pip` explicitly to the `conda create` invocation.

Author: malfet

.github/actions/setup-binary-builds/action.yml

@@ -113,7 +113,7 @@ runs:
           conda create \
             --yes --quiet \
             --prefix "${CONDA_ENV}" \
-            "python=3.9"
+            "python=3.9" pip
           CONDA_ENV="${CONDA_ENV}"
           CONDA_RUN="conda run --no-capture-output -p ${CONDA_ENV}"
           ${CONDA_RUN} python -m pip install ${GITHUB_WORKSPACE}/test-infra/tools/pkg-helpers