minor symfony#52380 [Tests] Add array return type for provider methods (OskarStark)

This PR was merged into the 5.4 branch.

Discussion
----------

[Tests] Add `array` return type for provider methods

| Q             | A
| ------------- | ---
| Branch?       | 5.4
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Issues        | --
| License       | MIT

Commits
-------

f317987 [Tests] Add `array` return type for provider methods

Author: nicolas-grekas

src/Symfony/Component/Form/Tests/Extension/Core/DataTransformer/DateTimeToRfc3339TransformerTest.php

@@ -43,12 +43,12 @@ public static function allProvider(): array
         ];
     }
 
-    public static function transformProvider()
+    public static function transformProvider(): array
     {
         return self::allProvider();
     }
 
-    public static function reverseTransformProvider()
+    public static function reverseTransformProvider(): array
     {
         return array_merge(self::allProvider(), [
             // format without seconds, as appears in some browsers
@@ -126,7 +126,7 @@ public function testReverseTransformExpectsValidDateString($date)
         $transformer->reverseTransform($date);
     }
 
-    public static function invalidDateStringProvider()
+    public static function invalidDateStringProvider(): array
     {
         return [
             'invalid month' => ['2010-2010-01'],