Update doctrine.rst

In 'Deleting an Object' you are not going to delete the entity itself but the given object.
minor #4053 Update doctrine.rst (sr972)

This PR was submitted for the master branch but it was merged into the 2.3 branch instead (closes #4053).

Discussion
----------

Update doctrine.rst

| Q             | A
| ------------- | ---
| Doc fix?      | [yes]
| New docs?     | [no]
| Applies to    | [2.3+]

In 'Deleting an Object' you are not going to delete the entity itself but the given object.

Commits
-------

b269ff0 Update doctrine.rst