Merge #17249: rpc: Add missing deque include to fix build

a592913022 http: add missing header bootlegged by boost < 1.72 (Jan Beich)

Pull request description:

  Regressed by boostorg/filesystem@9a14c37d6f. See [error log](https://github.com/bitcoin/bitcoin/files/3772177/bitcoin-0.18.1.log).

  ```c++
  httpserver.cpp:74:10: error: no template named 'deque' in namespace 'std'
      std::deque<std::unique_ptr<WorkItem>> queue;
      ~~~~~^
  ```

ACKs for top commit:
  laanwj:
    ACK a592913022

Tree-SHA512: fb0aee6a698c7aaa6a73baad7adc4f891be573af0d3cf6f4f59bc825afe5c0bc439c668077ff1990a6135522a0533a1a867430eebad28f0ade93fd79a95e179b

src/httpserver.cpp

@@ -15,6 +15,7 @@
 #include <sync.h>
 #include <ui_interface.h>
 
+#include <deque>
 #include <memory>
 #include <stdio.h>
 #include <stdlib.h>