adjust example exception behavior to match latest spec

examples/broadcast_server/broadcast_server.cpp

@@ -67,10 +67,6 @@ public:
             m_server.run();
         } catch (const std::exception & e) {
             std::cout << e.what() << std::endl;
-        } catch (websocketpp::lib::error_code e) {
-            std::cout << e.message() << std::endl;
-        } catch (...) {
-            std::cout << "other exception" << std::endl;
         }
     }
 
@@ -154,7 +150,7 @@ int main() {
 
     t.join();
 
-    } catch (std::exception & e) {
+    } catch (websocketpp::exception const & e) {
         std::cout << e.what() << std::endl;
     }
 }