Update grammars to Rust 2021 edition

Author: Luni-4

tree-sitter-ccomment/Cargo.toml

@@ -8,7 +8,7 @@ readme = "bindings/rust/README.md"
 keywords = ["incremental", "parsing", "ccomment"]
 categories = ["parsing", "text-editors"]
 repository = "https://github.com/mozilla/rust-code-analysis"
-edition = "2018"
+edition = "2021"
 
 build = "bindings/rust/build.rs"
 include = [

tree-sitter-mozcpp/Cargo.toml

@@ -8,7 +8,7 @@ readme = "bindings/rust/README.md"
 keywords = ["incremental", "parsing", "mozcpp"]
 categories = ["parsing", "text-editors"]
 repository = "https://github.com/mozilla/rust-code-analysis"
-edition = "2018"
+edition = "2021"
 
 build = "bindings/rust/build.rs"
 include = [

tree-sitter-mozjs/Cargo.toml

@@ -8,7 +8,7 @@ readme = "bindings/rust/README.md"
 keywords = ["incremental", "parsing", "mozjs"]
 categories = ["parsing", "text-editors"]
 repository = "https://github.com/mozilla/rust-code-analysis"
-edition = "2018"
+edition = "2021"
 
 build = "bindings/rust/build.rs"
 include = [

tree-sitter-preproc/Cargo.toml

@@ -8,7 +8,7 @@ readme = "bindings/rust/README.md"
 keywords = ["incremental", "parsing", "preproc"]
 categories = ["parsing", "text-editors"]
 repository = "https://github.com/mozilla/rust-code-analysis"
-edition = "2018"
+edition = "2021"
 
 build = "bindings/rust/build.rs"
 include = [