fixed comment in forms.xml file
minor #10514 [FrameworkBundle] fixed comment in forms.xml file (hhamon)

This PR was merged into the 2.3 branch.

Discussion
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[FrameworkBundle] fixed comment in forms.xml file

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | ~
| License       | MIT
| Doc PR        | ~

Commits
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f9f7246 [FrameworkBundle] fixed comment in forms.xml file