Remove duplicate addition of preferences item

After change I7ec4a0be the "Show Change Number In Changes Table" is
being added to the grid twice.

This does not result in the item being displayed twice.  It is only
displayed once, but has an empty table row above it.

Change-Id: I76cdcdb7931e3a2c8e2eb465f40d2d7abbc91bf8
1 file changed