Merge branch 'mraszyk/httpbin-connection-close' into 'master'

Reducing test flakiness: add Connection: close header to httpbin server

The header `Connection: close` is supposed to prevent the client (https outcalls adapter in this case) from keeping idle connections alive as they're not being kept alive on the httpbin server.

This is supposed to **reduce** system test **flakiness** due to reusing connections believed to be alive by the replica that are already closed on the httpbin server. 

See merge request dfinity-lab/public/ic!12497

Author: marko-k0

WORKSPACE.bazel

@@ -437,8 +437,8 @@ http_archive(
 package(default_visibility = ["//visibility:public"])
 filegroup(name = "artifacts", srcs = glob(["build/*", "test-data/*"]), visibility = ["//visibility:public"])
       """,
-    sha256 = "f91fed3158779b32310e5cf7bcdf7915b38eaf635a72a52c844f656806e3e5d6",
-    urls = ["https://download.dfinity.systems/ic-ref/ic-ref-test-0.0.1-5fc27bdc-x86_64-linux.tar.gz"],
+    sha256 = "6ae6664fc6f5879b7ca9f7a1f3262c9a2d6f0118238759d222049a29b4c523b4",
+    urls = ["https://download.dfinity.systems/ic-ref/ic-ref-test-0.0.1-a1b3f670-x86_64-linux.tar.gz"],
 )
 
 # Deployed NNS canisters

rs/tests/httpbin-rs/src/main.rs

@@ -67,6 +67,8 @@ impl Response {
         ));
     }
     fn set_aux_headers(&mut self) {
+        self.headers
+            .push(("Connection".to_string(), "close".to_string()));
         self.headers
             .push(("Access-Control-Allow-Origin".to_string(), "*".to_string()));
         self.headers.push((