Move networkx and portpicker to extras under "spanner-graph-notebook".

Author: ericfe-google

setup.py

@@ -33,10 +33,8 @@
     "ipywidgets>=7.7.1",
     "ipython>=7.23.1",
     "ipykernel>=5.5.6",
-    "networkx",
     "packaging >= 20.0.0",
-    "pandas>=1.1.0",
-    "portpicker",
+    "pandas>=1.1.0",    
     "pyarrow >= 3.0.0",
     "pydata-google-auth >=1.5.0",
     "tqdm >= 4.7.4, <5.0.0dev",
@@ -58,7 +56,7 @@
     ],
     "bigframes": ["bigframes >= 1.17.0"],
     "geopandas": ["geopandas >= 1.0.1"],
-    "spanner-graph-notebook": ["spanner-graph-notebook >= 1.1.1"],
+    "spanner-graph-notebook": ["spanner-graph-notebook >= 1.1.1", "networkx", "portpicker",],
 }
 
 all_extras = []