minor #30112 Remove "internal" annotation from datacollector serialization methods (nicolas-grekas)

This PR was merged into the 3.4 branch.

Discussion
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Remove "internal" annotation from datacollector serialization methods

| Q             | A
| ------------- | ---
| Branch?       | 3.4
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

I've been a bit too aggressively adding `@internal` in #30035.

Commits
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3c8fd2072f Remove "internal" annotation from datacollector serialization methods

Author: nicolas-grekas

Extension/DataCollector/FormDataCollector.php

@@ -228,9 +228,6 @@ public function getData()
         return $this->data;
     }
 
-    /**
-     * @internal
-     */
     public function serialize()
     {
         if ($this->hasVarDumper) {