reqs: allow xmltodict 0.13

I tried and tried, but couldn't find any reason not to allow the newer
version of xmltodict now that we no longer support Python 2.

Author: dgw

pyproject.toml

@@ -32,7 +32,7 @@ classifiers = [
 ]
 requires-python = ">=3.7"
 dependencies = [
-    "xmltodict==0.12",
+    "xmltodict<0.14",
     "pytz",
     "praw>=4.0.0,<8.0.0",
     "geoip2>=4.0,<5.0",