ext4: correct documentation for grpid mount option

The grpid option is currently described as being the same as nogrpid.
Signed-off-by: NErnesto A. Fernández <ernesto.mnd.fernandez@gmail.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org

Documentation/filesystems/ext4.txt

@@ -233,7 +233,7 @@ data_err=ignore(*)	Just print an error message if an error occurs
 data_err=abort		Abort the journal if an error occurs in a file
 			data buffer in ordered mode.
 
-grpid			Give objects the same group ID as their creator.
+grpid			New objects have the group ID of their parent.
 bsdgroups
 
 nogrpid		(*)	New objects have the group ID of their creator.