Update ADD_TO_EXISTING_PACKAGE.md

Co-authored-by: Stefan Verhoeven <stefan.verhoeven@gmail.com>

Author: eriktks

ADD_TO_EXISTING_PACKAGE.md

@@ -21,7 +21,6 @@ $ git merge existing_code/<BRANCH> --allow-unrelated-histories
 4. The previous step will likely result in several merge conflicts. Solve the conflicts by editing the files.
 5. Add all the files to GitHub:
 ```shell
-$ EDITOR CONFLICT_FILES
 $ git add --all
 $ git commit -m "Merged existing code with code generated by `cookiecutter https://github.com/NLeSC/python-template`"
 $ git push