fix typo (#691)

Author: ocefpaf

CHANGES.txt

@@ -15,7 +15,7 @@
 API changes
 
 - All popups are considered HTML text by default (ocefpaf #689)
-  If a popup requires rendering use the `karg` `parse_html=True`.
+  If a popup requires rendering use the `kwarg` `parse_html=True`.
 - `Circle` and `CircleMarker` are set to leaflet's defaults and accepted all
   `Path` optional arguments (# 683)
 - Changed default `max_bounds` to `False` to reflect leaflet's default value (rdd9999 #641)