replace "format" with f string (#1725)

Co-authored-by: Mark Saroufim <marksaroufim@fb.com>
Co-authored-by: Holly Sweeney <77758406+holly1238@users.noreply.github.com>

Author: 3 people

beginner_source/basics/buildmodel_tutorial.py

@@ -38,7 +38,7 @@
 # continue to use the CPU.
 
 device = 'cuda' if torch.cuda.is_available() else 'cpu'
-print('Using {} device'.format(device))
+print(f'Using {device} device')
 
 ##############################################
 # Define the Class