update cellpop import to pypi (to fix pandas issue)

src/user_templates_api/templates/jupyter_lab/templates/scalable_cell_populations/template.txt

@@ -17,7 +17,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "!pip install -i https://test.pypi.org/simple/ cellpop==0.1.0\n",
+    "!pip install cellpop==0.1.0\n",
     "!pip install hubmap-template-helper"
    ]
   },