pin python 3.9 in nightly push (#3009)

* lock python versin in conda

* set python 3.9

---------

Co-authored-by: Ankith Gunapal <agunapal@ischool.Berkeley.edu>

Author: lxning

.github/workflows/torchserve-nightly-build.yml

@@ -13,7 +13,7 @@ jobs:
         with:
           activate-conda: true
           update-conda: false
-          python-version: 3.10
+          python-version: "3.9"
       - run: conda --version
       - run: conda install -y conda-build anaconda-client
       - name: Checkout TorchServe