[keyvalut] Enhance code style for sample file

Modernize to follow with up-to-date coding style for
sdk/keyvault/azure-keyvault-keys/samples/list_operations.py
- change format to f-string

Closes: Azure#6

sdk/keyvault/azure-keyvault-keys/samples/list_operations.py

@@ -45,8 +45,8 @@
 print("\n.. Create Key")
 rsa_key = client.create_rsa_key("rsaKeyName")
 ec_key = client.create_ec_key("ecKeyName")
-print("Key with name '{0}' was created of type '{1}'.".format(rsa_key.name, rsa_key.key_type))
-print("Key with name '{0}' was created of type '{1}'.".format(ec_key.name, ec_key.key_type))
+print(f"Key with name '{rsa_key.name}' was created of type '{rsa_key.key_type}'.")
+print(f"Key with name '{ec_key.name}' was created of type '{ec_key.key_type}'.")
 
 # You need to check the type of all the keys in the vault.
 # Let's list the keys and print their key types.
@@ -57,20 +57,20 @@
 for key in keys:
     retrieved_key = client.get_key(key.name)
     print(
-        "Key with name '{0}' with type '{1}' was found.".format(retrieved_key.name, retrieved_key.key_type)
+        f"Key with name '{retrieved_key.name}' with type '{retrieved_key.key_type}' was found."
     )
 
 # The rsa key size now should now be 3072, default - 2048. So you want to update the key in Key Vault to ensure
 # it reflects the new key size. Calling create_rsa_key on an existing key creates a new version of the key in
 # the Key Vault with the new key size.
 new_key = client.create_rsa_key(rsa_key.name, size=3072)
-print("New version was created for Key with name '{0}' with the updated size.".format(new_key.name))
+print(f"New version was created for Key with name '{new_key.name}' with the updated size.")
 
 # You should have more than one version of the rsa key at this time. Lets print all the versions of this key.
 print("\n.. List versions of a key using its name")
 key_versions = client.list_properties_of_key_versions(rsa_key.name)
 for key in key_versions:
-    print("Key '{0}' has version: '{1}'".format(key.name, key.version))
+    print(f"Key '{key.name}' has version: '{key.version}'")
 
 # Both the rsa key and ec key are not needed anymore. Let's delete those keys.
 print("\n.. Delete the created keys...")
@@ -81,4 +81,4 @@
 print("\n.. List deleted keys from the Key Vault (requires soft-delete)")
 deleted_keys = client.list_deleted_keys()
 for deleted_key in deleted_keys:
-    print("Key with name '{0}' has recovery id '{1}'".format(deleted_key.name, deleted_key.recovery_id))
+    print(f"Key with name '{deleted_key.name}' has recovery id '{deleted_key.recovery_id}'")