[5.2] use _JEXEC for restricted access

[heelc29]

Summary of Changes

replace check of constant from JPATH_BASE to _JEXEC for restricted access
like other files eg.

joomla-cms/installation/src/Form/Rule/PrefixRule.php

Lines 14 to 16 in f2b1145

	// phpcs:disable PSR1.Files.SideEffects
	\defined('_JEXEC') or die;
	// phpcs:enable PSR1.Files.SideEffects

Testing Instructions

code review

Actual result BEFORE applying this Pull Request

JPATH_BASE is used for check of restricted access

Expected result AFTER applying this Pull Request

JPATH_BASE is not used for check of restricted access

Link to documentations

Please select:

• No documentation changes for docs.joomla.org needed
• No documentation changes for manual.joomla.org needed

[Quy]

I have tested this item ✅ successfully on b8a737b

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/44193.}

[richard67]

I have tested this item ✅ successfully on b8a737b

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/44193.}

[richard67]

RTC

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/44193.}

[heelc29]

Rebased to 5.2-dev

[pe7er]

Thanks @heelc29 !