Cleanup of licences and advisories (#550)

* We no longer ship any MPL licenced content, so removed it, since if we
 do encounter it again, it should be included with the image as source.
* We don't have any CC0-1.0 either, so removed it.
* The advisories that we were ignoring, are no longer an issue, so
removed as well.
* No longer using slog-json, so removed that exception.
* Added `Unicode-DFS-2016` as an allowed licence, since `unicode-ident`
 is using it in a latest release.

about.toml

@@ -18,7 +18,6 @@ accepted = [
     "Apache-2.0",
     "BSD-2-Clause",
     "BSD-3-Clause",
-    "CC0-1.0",
     "MIT",
-    "MPL-2.0",
+    "Unicode-DFS-2016",
 ]

deny.toml

@@ -14,13 +14,8 @@
 # limitations under the License.
 #
 
-# Only affects local time, and we only depend on time 0.1 and chrono through slog,
-# which we're moving away from.
 [advisories]
-ignore = [
-    "RUSTSEC-2020-0071",
-    "RUSTSEC-2020-0159",
-]
+ignore = []
 
 # This section is considered when running `cargo deny check licenses`
 # More documentation for the licenses section can be found here:
@@ -32,5 +27,4 @@ default = "allow"
 exceptions = [
     # Each entry is the crate and version constraint, and its specific allow
     # list
-    { allow = ["MPL-2.0"], name = "slog-json", version = "*" },
 ]