mycroft-config using deprecated --tempfile when falling back to nano

[smokejohn]

Describe the bug
In the case where mycroft-config tries to use nano because sensible-editor is not available on the system it uses the deprecated --tempfile parameter which newer versions of nano don't recognize anymore.

To Reproduce
Steps to reproduce the behavior:

1. Fresh install ArchLinuxARM-rpi-armv7-latest or any system without sensible-editor and nano >= 5.0
2. mycroft-config edit user
3. nano doesn't start and prints error about unrecognized option

nano: unrecognized option '--tempfile'
Type 'nano -h' for a list of available options.
Configuration unchanged.

Expected behavior
Open mycroft config with nano without erroring out.

Fix

• replace deprecated --tempfile with --saveonexit
• https://www.nano-editor.org/news.php (was deprecated and changed on July 29, 2020)

Environment:

• Device type: Raspberry PI 3b
• OS: ArchLinuxARM-rpi-armv7-latest
• Mycroft-core version: [21, 2, 2]