fix: configuration error on cargo-deny

see: [Add version = 2 by Jake-Shadle · Pull Request #611 · EmbarkStudios/cargo-deny](EmbarkStudios/cargo-deny#611)

previously
```
warning[deprecated]: this key will be removed in a future update, see EmbarkStudios/cargo-deny#611 for details
   ┌─ /mnt/nvme0n1p1/david/src/github.com/cdevents/sdk-rust/tools/cargo-deny/deny.toml:22:1
   │
22 │ vulnerability = "deny"
   │ ^^^^^^^^^^^^^

warning[deprecated]: this key will be removed in a future update, see EmbarkStudios/cargo-deny#611 for details
   ┌─ /mnt/nvme0n1p1/david/src/github.com/cdevents/sdk-rust/tools/cargo-deny/deny.toml:21:1
   │
21 │ unmaintained = "deny"
   │ ^^^^^^^^^^^^

warning[deprecated]: this key will be removed in a future update, see EmbarkStudios/cargo-deny#611 for details
  ┌─ /mnt/nvme0n1p1/david/src/github.com/cdevents/sdk-rust/tools/cargo-deny/deny.toml:9:1
  │
9 │ unlicensed = "deny"
  │ ^^^^^^^^^^

warning[deprecated]: this key will be removed in a future update, see EmbarkStudios/cargo-deny#611 for details
   ┌─ /mnt/nvme0n1p1/david/src/github.com/cdevents/sdk-rust/tools/cargo-deny/deny.toml:10:1
   │
10 │ copyleft = "deny"
   │ ^^^^^^^^

warning[license-not-encountered]: license was not encountered
   ┌─ /mnt/nvme0n1p1/david/src/github.com/cdevents/sdk-rust/tools/cargo-deny/deny.toml:12:32
   │
12 │ allow = ["Apache-2.0", "MIT", "BSD-2-Clause", "Unicode-DFS-2016"]
   │                                ^^^^^^^^^^^^ unmatched license allowance

advisories ok, licenses ok
```

Signed-off-by: David Bernard <david.bernard.31@gmail.com>

Author: davidB

tools/cargo-deny/deny.toml

@@ -6,10 +6,8 @@ multiple-versions = "deny"
 wildcards = "deny"
 
 [licenses]
-unlicensed = "deny"
-copyleft = "deny"
 confidence-threshold = 0.95
-allow = ["Apache-2.0", "MIT", "BSD-2-Clause", "Unicode-DFS-2016"]
+allow = ["Apache-2.0", "MIT", "Unicode-DFS-2016"]
 exceptions = []
 
 # The unpublished packages (generator) would be ignored now
@@ -18,8 +16,6 @@ exceptions = []
 ignore = true
 
 [advisories]
-unmaintained = "deny"
-vulnerability = "deny"
 yanked = "warn"
 # Users who require or prefer Git to use SSH cloning instead of HTTPS,
 # such as implemented via "insteadOf" rules in Git config, can still