Add volla proprietary license

[pombredanne]

See https://github.com/HelloVolla/volla-chat/blob/release-script/LICENSE.txt
It seems to have some limited usage: https://github.com/search?q="Volla+Licence+1.0"&type=code

[DennisClark]

New license LicenseRef-scancode-volla-1.0 created in DejaCode enterprise and public. Proprietary Free. Personal, non-commercial use only. Not suitable for product usage.

@AyanSinhaMahapatra Please synchronize when you have time, thanks.

[AyanSinhaMahapatra]

Added in #4278, added also to licensedb and license-expression v30.4.4 , closing.