Update sopel/irc/isupport.py

Co-Authored-By: dgw <dgw@technobabbl.es>

sopel/irc/isupport.py

@@ -148,7 +148,7 @@ class ISupport(object):
     """Storage class for IRC's ``ISUPPORT`` feature.
 
     An instance of ``ISupport`` can be used as a read-only dict, to store
-    feature advertised by the IRC server::
+    features advertised by the IRC server::
 
         >>> isupport = ISupport(chanlimit=(('&', None), ('#', 70)))
         >>> isupport['CHANLIMIT']