Update pull_requests.rst

Co-authored-by: Christian Flothmann <christian.flothmann@gmail.com>

Author: OskarStark

contributing/code/pull_requests.rst

@@ -150,7 +150,7 @@ work:
 During the :ref:`stabilization phase <contributing-release-development>`, the development branch is in
 feature freeze. Please help the community prepare for the new version release. If you want to submit a
 new feature pull request, you should target the next version. For example, if ``6.3`` reached feature
-freeze, new features should target ``6.4``. If the ``6.4`` branch does not yet exists, target ``6.3``
+freeze, new features should target ``6.4``. If the ``6.4`` branch does not yet exist, target ``6.3``
 and rebase your pull requests once the branch is created.
 
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