Fix checking the wrong variable

This was not checking against the new vector for metrics tables, so it
was wrong about what were system reads vs. regular ones.

Fixing the table makes it work properly and also verified locally that
this now updates rows read correctly.

Author: dbussink

storage/innobase/dict/mem.cc

@@ -191,7 +191,7 @@ static bool dict_mem_table_is_system_metrics(const std::string &name) {
   if (name.find('/') == std::string::npos)
     return true;
 
-  for (auto p : innobase_system_databases) {
+  for (auto p : innobase_system_databases_metrics) {
     if (name.length() > p.length() && name.compare(0, p.length(), p) == 0)
       return true;
   }