Fix URL excludes loading (sopel-irc#959)

setup uses it as a list, and in previous versions of sopel it was a list, but in the UrlSection it's defined as a ValidatedAttribute. This was causing each character in the excludes list to be parsed as a regex exclude. Switching to ListAttribute fixes the issue.

sopel/modules/url.py

@@ -10,7 +10,7 @@
 import re
 from sopel import web, tools
 from sopel.module import commands, rule, example
-from sopel.config.types import ValidatedAttribute, StaticSection
+from sopel.config.types import ValidatedAttribute, ListAttribute, StaticSection
 
 
 url_finder = None
@@ -29,7 +29,7 @@
 
 class UrlSection(StaticSection):
     # TODO some validation rules maybe?
-    exclude = ValidatedAttribute('exclude')
+    exclude = ListAttribute('exclude')
     exclusion_char = ValidatedAttribute('exclusion_char', default='!')