web: Update to Rust 2021 edition

Author: Luni-4

rust-code-analysis-web/Cargo.toml

@@ -2,7 +2,7 @@
 name = "rust-code-analysis-web"
 version = "0.0.23"
 authors = ["Calixte Denizet <cdenizet@mozilla.com>"]
-edition = "2018"
+edition = "2021"
 repository = "https://github.com/mozilla/rust-code-analysis/tree/master/rust-code-analysis-web"
 keywords = ["metrics"]
 description = "Run a web service to compute and export code metrics"