Merge pull request #21112 from kamipo/fix_mysql2_version

Should use `server_info[:version]` instead of `info[:version]`

activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb

@@ -273,7 +273,7 @@ module ActiveRecord
       end
 
       def full_version
-        @full_version ||= @connection.info[:version]
+        @full_version ||= @connection.server_info[:version]
       end
 
       def set_field_encoding field_name