Drop no longer needed warning suppression for clang

74345c92e4 fixed the underlying problem
for Python, and it was fixed for other affected languages shortly
after - see https://github.com/swig/swig/pull/1027

Examples/test-suite/li_std_vector_extra.i

@@ -12,17 +12,6 @@
 #include <algorithm>
 #include <functional>
 #include <numeric>
-
-
-#if defined(__clang__)
-// Suppress:
-// warning: destination for this 'memset' call is a pointer to dynamic class
-//       'Test::B'; vtable pointer will be overwritten [-Wdynamic-class-memaccess]
-//         memset(v_def,0,sizeof(Type));
-// Better generated code is probably needed though
-#pragma clang diagnostic ignored "-Wdynamic-class-memaccess"
-#endif
-
 %}
 
 namespace std {