Fix Sieve: Do not allow invalid certs in http_header function

crates/common/src/scripts/plugins/http.rs

@@ -26,11 +26,15 @@ pub async fn exec_header(ctx: PluginContext<'_>) -> trc::Result<Variable> {
         return Ok(Variable::from(url.split_once("/?").unwrap().1.to_string()));
     }
 
-    reqwest::Client::builder()
+    let builder = reqwest::Client::builder()
         .user_agent(agent.as_ref())
         .timeout(Duration::from_millis(timeout))
-        .redirect(Policy::none())
-        .danger_accept_invalid_certs(true)
+        .redirect(Policy::none());
+
+    #[cfg(feature = "test_mode")]
+    let builder = builder.danger_accept_invalid_certs(true);
+
+    builder
         .build()
         .map_err(|err| {
             trc::SieveEvent::RuntimeError