minor #11804 Add weeks in the options 'labels' (SulivanDotEu)

This PR was submitted for the 4.3 branch but it was merged into the 3.4 branch instead (closes #11804).

Discussion
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Add weeks in the options 'labels'

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Hi there,

In the documentation about [DateIntervalType](https://symfony.com/doc/current/reference/forms/types/dateinterval.html#labels), weeks is missing from the code example. I added it to avoid any confusion.

It is my first contribution, not very familiar with all the tools.

Commits
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828ff37 Add weeks in the options 'labels'

Author: javiereguiluz

reference/forms/types/dateinterval.rst

@@ -146,6 +146,7 @@ are ``null``, so they display the "humanized version" of the child names (``Inve
         'invert' => null,
         'years' => null,
         'months' => null,
+        'weeks' => null,
         'days' => null,
         'hours' => null,
         'minutes' => null,