Update the name of the update_tags utility in the git mirror how-to.

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@381398 65c4cc65-6c06-0410-ace0-fbb531ad65f3

include/asterisk/doxygen/asterisk-git-howto.h

@@ -108,7 +108,7 @@
  * If you don't like the extra 'v', just edit the sed command.
  *
  \verbatim
-  ../asterisk-tools/update-tags
+  ../asterisk-tools/update_tags
  \endverbatim
  * 
  * Example configuration (refer to menuselect/menuselelct for more