Remove redundant rename statement in changehc

Author: chinandrew

changehc/delphi_changehc/update_sensor.py

@@ -229,7 +229,7 @@ def update_sensor(self,
         # sample size is never shared
         df["sample_size"] = np.nan
         # conform to naming expected by create_export_csv()
-        df = df.reset_index().rename(columns={"date": "timestamp", "rate": "val"})
+        df = df.reset_index().rename(columns={"rate": "val"})
         # df.loc[~df['incl'], ["val", "se"]] = np.nan  # update to this line after nancodes get merged in
         df = df[df['incl']]