keyword: use all caps for 'note:' in help string

The diff, export, log, and status commands write it as 'NOTE:'.

hgext/keyword.py

@@ -45,8 +45,8 b' Example:'
     **.py =
     x*    = ignore
 
-Note: the more specific you are in your filename patterns the less you lose
-      speed in huge repositories.
+NOTE: the more specific you are in your filename patterns the less you lose
+speed in huge repositories.
 
 For [keywordmaps] template mapping and expansion demonstration and control run
 "hg kwdemo".

tests/test-keyword.out

@@ -18,8 +18,8 b' Example:'
     **.py =
     x*    = ignore
 
-Note: the more specific you are in your filename patterns the less you lose
-      speed in huge repositories.
+NOTE: the more specific you are in your filename patterns the less you lose
+speed in huge repositories.
 
 For [keywordmaps] template mapping and expansion demonstration and control run
 "hg kwdemo".