Add missing <numeric> include (#3719)

include/nlohmann/detail/exceptions.hpp

@@ -10,6 +10,9 @@
 
 #include <cstddef> // nullptr_t
 #include <exception> // exception
+#if JSON_DIAGNOSTICS
+    #include <numeric> // accumulate
+#endif
 #include <stdexcept> // runtime_error
 #include <string> // to_string
 #include <vector> // vector