text: Title: ViewSet filter date picker missing margin
  Body: <!--
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  ### Issue Summary
  filtering a snippet by date shows the date field missing margins on one side.
  ![image](https://github.com/user-attachments/assets/89338c52-3e20-4b98-9ac0-2bc9c0008d2e)
  
  <!--
  A summary of the issue.
  -->
  
  ### Steps to Reproduce
  I am using the model BreadPage from the bakery demo as a ModelViewSet to demo this issue since the other viewsets do not make use of any date fields.
  
  1. In bakery demo bakerydemo > breads > wagtail_hooks.py 
  
  Add the following to the bottom
  ```python
  from bakerydemo.breads.models import BreadPage
  class ExampleModelViewSet(ModelViewSet):
      model = BreadPage
      add_to_admin_menu = True
  
      panels = [
          FieldPanel("title"),
      ]
      list_filter = ["last_published_at"]
  
  register_snippet(ExampleModelViewSet)
  ```
  2. in the admin sidebar click Bread Pages
  3. Click filter options > Last published at. It will show below
  ![image](https://github.com/user-attachments/assets/01f4e069-8df0-4f4b-8715-528c5d1c2ad1)
  
  
  Any other relevant information. For example, why do you consider this a bug and what did you expect to happen instead?
  
  -   I have confirmed that this issue can be reproduced as described on a fresh Wagtail project: yes
  
  ### Technical details
  
  -   Wagtail version: 6.3 (dev)
  ### Working on this
  
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