refactor(http1): resolve collapsible_match lint

Collapse the nested `if` inside the `Version::HTTP_11`
match arm into a match guard.

Refs #4071

Author: nakaryo716

Cargo.toml

@@ -118,7 +118,6 @@ as_conversions = "allow" # TODO: tricky
 cast_possible_truncation = "allow" # TODO: consider
 cast_precision_loss = "allow" # TODO: consider
 checked_conversions = "allow"
-collapsible_match = "allow"
 else_if_without_else = "allow"
 enum_glob_use = "allow"
 float_arithmetic = "allow"

src/proto/h1/conn.rs

@@ -676,11 +676,9 @@ where
                 Version::HTTP_10 => self.state.disable_keep_alive(),
                 // If response is version 1.1 and keep-alive is wanted, add
                 // Connection: keep-alive header when not present
-                Version::HTTP_11 => {
-                    if self.state.wants_keep_alive() {
-                        head.headers
-                            .insert(CONNECTION, HeaderValue::from_static("keep-alive"));
-                    }
+                Version::HTTP_11 if self.state.wants_keep_alive() => {
+                    head.headers
+                        .insert(CONNECTION, HeaderValue::from_static("keep-alive"));
                 }
                 _ => (),
             }