f-stirng modify sample/backup_restore_operations_async.py

[KdHyeon0661]

Is your feature request related to a problem? Please describe.
Replace str.format() with another method to improve the readability of source code.

Describe the solution you'd like
Change str.format() formatting of the source code to f-string formatting.

Describe alternatives you've considered
Before:
print("Key with name '{0}' created with key type '{1}'".format(key.name, key.key_type))

After:
print(f"Key with name '{key.name}' created with key type '{key.key_type}'")

Additional context
x