Remove old FIXME comment from reiserfs::read_label()

Traced debugreiserfs on a 10GiB reiserfs file system which was 100% full
full with nearly 900,000 files.  It read exactly three 4KiB blocks from
different offsets and the program never took more than 0.1 seconds.

src/reiserfs.cc

@@ -107,7 +107,6 @@ void reiserfs::set_used_sectors( Partition & partition )
 
 void reiserfs::read_label( Partition & partition )
 {
-	//FIXME: i think running debugreiserfs takes a long time on filled file systems, test for this...
 	if ( ! Utils::execute_command( "debugreiserfs " + partition .get_path(), output, error, true ) )
 	{
 		partition .label = Utils::regexp_label( output, "^label:[\t ]*(.*)$" ) ;