Update gpo_member_photos.py

Another URL change to unitedstates.github.io.

scripts/gpo_member_photos.py

@@ -71,7 +71,7 @@ def get_legislators_current(br, include_historical=False):
     ).json()
     if include_historical:
         historical = br.get(
-            "https://theunitedstates.io/congress-legislators/"
+            "https://unitedstates.github.io/congress-legislators/"
             "legislators-historical.json"
         ).json()
         legislators += historical