[4.0] com_content columns - BS4 migration

[ciar4n]

Pull Request for Issue # .

Summary of Changes

Migrates intro article columns to BS4

Testing Instructions

Apply patch and open 'featured' or 'category blog' article list. Try various number of columns in menu item settings (Layout tab).

Before

After

Documentation Changes Required

[ghost]

I have tested this item ✅ successfully on 524da96

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/15291.}

[rjcf18]

I have tested this item ✅ successfully on 524da96 as you can see in the following images:

Before patch:

After patch:

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/15291.}

[rjcf18]

I have tested this item ✅ successfully on 524da96

---

_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/15291.}

[ghost]

RTC after two successful tests.