replace "or" with ","
minor #4691 replace "or" with "," (timglabisch)

This PR was merged into the 2.3 branch.

Discussion
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replace "or" with ","

See https://github.com/symfony/symfony-docs/pull/4405#discussion_r22293277
Just spelling.

Commits
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a950888 replace "or" with ","
Update form_customization.rst

There are two code samples which are inconsistent which each other. I updated one of them.
minor #4689 Update form_customization.rst (rodrigorigotti)

This PR was submitted for the master branch but it was merged into the 2.3 branch instead (closes #4689).

Discussion
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Update form_customization.rst

This replaces a PR by @rodrigorigotti: https://github.com/symfony/symfony-docs/pull/4688. Many thanks to him!

Original PR description:

> There are two code samples which are inconsistent which each other. I updated one of them.

Commits
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4cd2046 Update form_customization.rst
Merge branch '2.3' into 2.5
Merge branch '2.5' into 2.6

Conflicts:
	cookbook/form/form_customization.rst
Merge branch '2.7'