Change io_service to io_context

This was renamed a while back in boost to be compliant with the
std::executors proposal.

Change-Id: Ic563e4e78b3c814037090606c51638868557327e
Signed-off-by: Ed Tanous <edtanous@google.com>
diff --git a/include/error_monitors/vr_hot_monitor.hpp b/include/error_monitors/vr_hot_monitor.hpp
index 81c684d..fe8aa39 100644
--- a/include/error_monitors/vr_hot_monitor.hpp
+++ b/include/error_monitors/vr_hot_monitor.hpp
@@ -39,7 +39,7 @@
     }
 
   public:
-    VRHotMonitor(boost::asio::io_service& io,
+    VRHotMonitor(boost::asio::io_context& io,
                  std::shared_ptr<sdbusplus::asio::connection> conn,
                  const std::string& signalName, const std::string& vrName) :
         BaseGPIOMonitor(io, conn, signalName, assertValue),