Remove unused fallback code from DiskLabel.
Remove unused fallback code from DiskLabel.

This is not used, and the partitions part would cause calling code
to fail anyway since it all expects a list of parted.Partition instances.

vojtechtrefny/blivet,vpodzime/blivet,rhinstaller/blivet,vpodzime/blivet,rvykydal/blivet,jkonecny12/blivet,dwlehman/blivet,jkonecny12/blivet,AdamWill/blivet,rhinstaller/blivet,dwlehman/blivet,AdamWill/blivet,rvykydal/blivet,vojtechtrefny/blivet