[5.1] Fix header translation for modal select field

[Fedik]

Pull Request for Issue #42918

Summary of Changes

Fix header translation for modal select field

Testing Instructions

Add following field XML, somewhere, example in Custom HTML module.

<field
  type="ModalSelect"
  name="article"
  label="Article"

  select="true"
  titleSelect="JGLOBAL_SELECT_AN_OPTION"
  urlSelect="index.php?option=com_content&amp;view=articles&amp;layout=modal&amp;tmpl=component"
  clear="true"
/>

Then edit the form with it, click "select" button.
Check the dialog heading.

Actual result BEFORE applying this Pull Request

The heading is untranslated language constant.

Expected result AFTER applying this Pull Request

The heading is translated

Link to documentations

Please select:

• Documentation link for docs.joomla.org:
• No documentation changes for docs.joomla.org needed
• Pull Request link for manual.joomla.org:
• No documentation changes for manual.joomla.org needed

[Quy]

I have tested this item ✅ successfully on 1ddceaf

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[ghost]

I have tested this item ✅ successfully on 1ddceaf

---

_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/43878.}

[Quy]

RTC

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/43878.}

[bembelimen]

Thx