minor symfony#25096 Incorrect dot on method loadChoices in upgrade doc (hugohenrique)

This PR was merged into the 4.1-dev branch.

Discussion
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Incorrect dot on method loadChoices in upgrade doc

| Q             | A
| ------------- | ---
| Branch?       | master / 2.7, 2.8, 3.3, or 3.4 <!-- see comment below -->
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| License       | MIT

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Commits
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0b84b83 Incorrect dot on method loadChoices in upgrade doc

Author: chalasr

UPGRADE-4.0.md

@@ -323,7 +323,7 @@ Form
    ```php
    class MyTimezoneType extends AbstractType
    {
-       public function. getParent()
+       public function getParent()
        {
            return TimezoneType::class;
        }