chore(gcp_pubsub): just deprecate `request_timeout` instead of removing

lib-ee/emqx_ee_bridge/i18n/emqx_ee_bridge_gcp_pubsub.conf

@@ -77,8 +77,8 @@ emqx_ee_bridge_gcp_pubsub {
 
     request_timeout {
         desc {
-          en: "HTTP request timeout."
+          en: "Deprecated: Configure the request timeout in the buffer settings."
-          zh: "HTTP 请求超时。"
+          zh: "废弃的。在缓冲区设置中配置请求超时。"
         }
         label: {
               en: "Request Timeout"

lib-ee/emqx_ee_bridge/src/emqx_ee_bridge_gcp_pubsub.erl

@@ -79,6 +79,16 @@ fields(bridge_config) ->
                     desc => ?DESC("max_retries")
                 }
             )},
+        {request_timeout,
+            sc(
+                emqx_schema:duration_ms(),
+                #{
+                    required => false,
+                    deprecated => {since, "e5.0.1"},
+                    default => <<"15s">>,
+                    desc => ?DESC("request_timeout")
+                }
+            )},
         {payload_template,
             sc(
                 binary(),