minor #491 Update generate_doctrine_form.rst (jezemery)
minor #491 Update generate_doctrine_form.rst (jezemery)

This PR was merged into the 3.0.x-dev branch.

Discussion
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Update generate_doctrine_form.rst

These are Symfony 3 docs, therefore I feel they should target Symfony 3 first, and older versions second as most of the rest of the documentation seems to. Happy to have feedback!

Commits
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5a1f05c Update generate_doctrine_form.rst

sensiolabs/SensioGeneratorBundle,sensiolabs/SensioGeneratorBundle