catch exceptions as const

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I93925bf34b4fec181a56d6524cbe9c6182a16b1f
diff --git a/http/routing.hpp b/http/routing.hpp
index d2a10b2..5d9c8e3 100644
--- a/http/routing.hpp
+++ b/http/routing.hpp
@@ -1204,7 +1204,7 @@
         {
             rules[ruleIndex]->handleUpgrade(req, res, std::move(adaptor));
         }
-        catch (std::exception& e)
+        catch (const std::exception& e)
         {
             BMCWEB_LOG_ERROR << "An uncaught exception occurred: " << e.what();
             res.result(boost::beast::http::status::internal_server_error);