minor symfony#29960 Fix heredoc (Stadly)

This PR was merged into the 3.4 branch.

Discussion
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Fix heredoc

| Q             | A
| ------------- | ---
| Branch?       | 3.4
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | none
| License       | MIT
| Doc PR        | none

A heredoc was erroneously a nowdoc.

Commits
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15f5f69 Fix heredoc

Author: fabpot

src/Symfony/Component/Translation/Tests/fixtures/extractor/translation.html.php

@@ -1,7 +1,7 @@
 This template is used for translation message extraction tests
 <?php echo $view['translator']->trans('single-quoted key'); ?>
 <?php echo $view['translator']->trans('double-quoted key'); ?>
-<?php echo $view['translator']->trans(<<<'EOF'
+<?php echo $view['translator']->trans(<<<EOF
 heredoc key
 EOF
 ); ?>