build(deps): bump fluent from 0.15.0 to 0.16.0

Bumps [fluent](https://github.com/projectfluent/fluent-rs) from 0.15.0 to 0.16.0.
- [Release notes](https://github.com/projectfluent/fluent-rs/releases)
- [Commits](https://github.com/projectfluent/fluent-rs/commits)

Signed-off-by: dependabot-preview[bot] <[email protected]>

Author: dependabot-preview[bot]

Cargo.lock

@@ -6,7 +6,7 @@ edition = "2018"
 
 [dependencies]
 lazy_static = "1.2.0"
-fluent = "0.15"
+fluent = "0.16"
 fluent-bundle = "0.6.0"
 fluent-syntax = "0.11.0"
 fluent-locale = "0.10.1"