console: Update to reflect new default value

The default value was changed from 10 minutes to disabled in commit
a4199f5e.
Signed-off-by: NDaniel Xu <dxu@dxuuu.xyz>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

Documentation/admin-guide/kernel-parameters.txt

@@ -641,8 +641,8 @@
 		For now, only VisioBraille is supported.
 
 	consoleblank=	[KNL] The console blank (screen saver) timeout in
-			seconds. Defaults to 10*60 = 10mins. A value of 0
-			disables the blank timer.
+			seconds. A value of 0 disables the blank timer.
+                       Defaults to 0.
 
 	coredump_filter=
 			[KNL] Change the default value for