bmcweb: Remove deprecatd ASIO interfaces

boost::asio::io_service is removed in leiu of io_context, which is a
closer match to the networking TS.  Move us to that implementatio.

This was an automated move using the following command:
git grep -l 'io_service' | xargs sed -i 's/io_service/io_context/g'

Change-Id: I46605521c01f79f86f6901ddf69ddc8c4bc24103
Signed-off-by: Ed Tanous <ed.tanous@intel.com>
diff --git a/src/kvm_websocket_test.cpp b/src/kvm_websocket_test.cpp
index 1ddaad9..40470a9 100644
--- a/src/kvm_websocket_test.cpp
+++ b/src/kvm_websocket_test.cpp
@@ -24,7 +24,7 @@
     BMCWEB_ROUTE(app, "/")([]() { return boost::beast::http::status::ok; });
     auto _ = async(std::launch::async, [&] { app.run(); });
     auto routes = app.getRoutes();
-    asio::io_service is;
+    asio::io_context is;
 
     {
         // Retry a couple of times waiting for the server to come up