Documentation/config.txt: default gc.aggressiveWindow is 250, not 10

The default for gc.aggressiveWindow has been 250 since 1c192f3
(gc --aggressive: make it really aggressive, 2007-12-06).

Signed-off-by: Jay Soffian <jaysoffian@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/Documentation/config.txt b/Documentation/config.txt
index 437b4ac..75b8afe 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -885,7 +885,7 @@
 gc.aggressiveWindow::
 	The window size parameter used in the delta compression
 	algorithm used by 'git gc --aggressive'.  This defaults
-	to 10.
+	to 250.
 
 gc.auto::
 	When there are approximately more than this many loose