sources: update deny.toml to version 2

[jpculp]

Description of changes:

Several keys have been deprecated in favor of the same default values we were specifying before. By removing them and adding version = 2 under licenses we will maintain the same behavior, but without the deprecation notices.

Testing done:

BEFORE

[cargo-make][1] INFO - Running Task: check-licenses
warning[deprecated]: this key will be removed in a future update, see https://github.com/EmbarkStudios/cargo-deny/pull/611 for details
  ┌─ /tmp/sources/deny.toml:2:1
  │
2 │ unlicensed = "deny"
  │ ^^^^^^^^^^

warning[deprecated]: this key will be removed in a future update, see https://github.com/EmbarkStudios/cargo-deny/pull/611 for details
  ┌─ /tmp/sources/deny.toml:6:1
  │
6 │ allow-osi-fsf-free = "neither"
  │ ^^^^^^^^^^^^^^^^^^

warning[deprecated]: this key will be removed in a future update, see https://github.com/EmbarkStudios/cargo-deny/pull/611 for details
  ┌─ /tmp/sources/deny.toml:5:1
  │
5 │ copyleft = "deny"
  │ ^^^^^^^^

warning[deprecated]: this key will be removed in a future update, see https://github.com/EmbarkStudios/cargo-deny/pull/611 for details
  ┌─ /tmp/sources/deny.toml:7:1
  │
7 │ default = "deny"
  │ ^^^^^^^

bans ok, licenses ok, sources ok

AFTER

[cargo-make][1] INFO - Running Task: check-licenses
bans ok, licenses ok, sources ok

Terms of contribution:

By submitting this pull request, I agree that this contribution is dual-licensed under the terms of both the Apache License, version 2.0, and the MIT license.

[larvacea]

As the "before" paragraph says, the changes to the tool's behavior are fully described in EmbarkStudios/cargo-deny#611.