Fix: resolve lint issues in DDP multi-GPU tutorial

Author: samithcsachi

beginner_source/ddp_series_multigpu.rst

@@ -202,7 +202,6 @@ Running the distributed training job
 Here's what the code looks like:
 
 .. code-block:: python
-
    
    def main(rank, world_size, total_epochs, save_every):
       ddp_setup(rank, world_size)
@@ -220,7 +219,6 @@ Here's what the code looks like:
       mp.spawn(main, args=(world_size, total_epochs, save_every,), nprocs=world_size)
 
 
-
 Further Reading
 ---------------