remove specifying format of date

mimic-iv/buildmimic/sqlite/import.py

@@ -50,7 +50,7 @@
 def process_dataframe(df: pd.DataFrame, subjects: t.Optional[t.List[int]] = None) -> pd.DataFrame:
     for c in df.columns:
         if c.endswith('time') or c.endswith('date'):
-            df[c] = pd.to_datetime(df[c], format='ISO8601')
+            df[c] = pd.to_datetime(df[c])
 
     if subjects is not None and 'subject_id' in df:
         df = df.loc[df['subject_id'].isin(subjects)]