Update docs/en/reference/basic-mapping.rst
Update docs/en/reference/basic-mapping.rst

Co-Authored-By: Andreas Braun <492632a1b0572b19118c472a1ff7eeab1c65927a@users.noreply.github.com>
malarzm/mongodb-odm,doctrine/mongodb-odm,malarzm/mongodb-odm,doctrine/mongodb-odm,alcaeus/mongodb-odm,alcaeus/mongodb-odm