chore: Replace deprecated utcnow()

manage.py

@@ -1,10 +1,10 @@
 #!/usr/bin/env python
 import csv
+import datetime
 import json
 import os
 import re
 from collections import defaultdict
-from datetime import datetime, timedelta
 
 import click
 import requests
@@ -262,9 +262,9 @@ def github_activity(user, days, start, end):
         end += "T23:59:59Z"
 
     if not start and days:
-        start = (datetime.utcnow() - timedelta(days=days)).strftime("%Y-%m-%dT%H:%M:%SZ")
+        start = (datetime.datetime.now(tz=datetime.UTC) - datetime.timedelta(days=days)).strftime("%Y-%m-%dT%H:%M:%SZ")
     if not end:
-        end = datetime.utcnow().strftime("%Y-%m-%dT%H:%M:%SZ")
+        end = datetime.datetime.now(tz=datetime.UTC).strftime("%Y-%m-%dT%H:%M:%SZ")
 
     query = format_string.format(
         queries='\n'.join(f'  user{i}: user(login: "{login}") {{\n    ...f\n  }}''' for i, login in enumerate(user)),