Allow lxml version 5 and newer

lxml 5 is now released and is the default version shipped on Fedora
versions 40 and above. The tests still pass if we use this version, and
there is nothing in the changelog that sounds like it would break our
usage, so removing this version constraing.

pyproject.toml

@@ -30,7 +30,7 @@ dependencies = [
     "requests>=2.27.1,<3",
     "python-dateutil>=2.8.1,<3",
     "botocore>=1.23.50,<2",
-    "lxml>=4.6.5,<5",
+    "lxml>=4.6.5",
     "zstandard>=0.21.0",
 ]