Given the following code:

final class WithStringKey
{
    public function getExtensions(): array
    {
        return [
            'a' => new FirstExtension(),
            'b' => new SecondExtension()
        ];
    }
}

currently got docblock:

+    /**
+     * @return \Rector\Tests\TypeDeclarationDocblocks\Rector\ClassMethod\AddReturnDocblockForCommonObjectDenominatorRector\Source\Contract\ExtensionInterface[]
+     */
     public function getExtensions(): array

which should use @return array<string, \Rector\Tests\TypeDeclarationDocblocks\Rector\ClassMethod\AddReturnDocblockForCommonObjectDenominatorRector\Source\Contract\ExtensionInterface>