git-completion.bash: lexical sorting for diff.statGraphWidth

df44483 (diff --stat: add config option to limit graph width,
2012-03-01) added the option diff.startGraphWidth to the list of
configuration variables in git-completion.bash, but failed to notice
that the list is sorted alphabetically.  Move it to its rightful place
in the list.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/completion/git-completion.bash

@@ -2054,13 +2054,13 @@ _git_config ()
 		core.whitespace
 		core.worktree
 		diff.autorefreshindex
-		diff.statGraphWidth
 		diff.external
 		diff.ignoreSubmodules
 		diff.mnemonicprefix
 		diff.noprefix
 		diff.renameLimit
 		diff.renames
+		diff.statGraphWidth
 		diff.suppressBlankEmpty
 		diff.tool
 		diff.wordRegex