Documentation: Fix skipped section level

With xmlto 0.0.18 it seems to demand that no section levels are
skipped.  The commit 'implement gitcvs.usecrlfattr' (8a06a63)
one such skip, which here is removed by increasing the level of the
offender.

Signed-off-by: Gustaf Hendeby <hendeby@isy.liu.se>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-cvsserver.txt

@@ -302,7 +302,7 @@ Legacy monitoring operations are not supported (edit, watch and related).
 Exports and tagging (tags and branches) are not supported at this stage.
 
 CRLF Line Ending Conversions
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 By default the server leaves the '-k' mode blank for all files,
 which causes the cvs client to treat them as a text files, subject