requirements: narrow requests to >=2.24

Sopel's other dependencies require requests>=24 at minimum, so there is
no sense in requiring only 2.0. Also, 2.0 is old, 2.24 is a good minimum
(and it's still compatible with 2.7).

requirements.txt

@@ -2,6 +2,6 @@ xmltodict==0.12
 pytz
 praw>=4.0.0,<6.0.0
 geoip2>=4.0,<5.0
-requests>=2.0.0,<3.0.0
+requests>=2.24.0,<3.0.0
 dnspython<3.0
 sqlalchemy>=1.4,<1.5