[OptionsResolver] Fix namespace
bug #4630 [OptionsResolver] Fix namespace (xavren)

This PR was merged into the 2.6 branch.

Discussion
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[OptionsResolver] Fix namespace

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | 2.6
| Fixed tickets | #4620

Commits
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1c24163 [OptionsResolver] Fix namespace