[TASK] Fix explanation of fourth parameter of FlashMessage (#1943)

Part of the explanation was duplicate and the second explanation
was under the severities and not within the explanation of the
constructor for FlashMessage.

Additionall, the names of the arguments are used instead of
line numbers, which makes it more clear and prevents problems
in case the snippet is modified or arguments removed.

Releases: main, 11.5

Documentation/ApiOverview/FlashMessages/Index.rst

@@ -47,18 +47,25 @@ of class :php:`\TYPO3\CMS\Core\Messaging\FlashMessage`
    use TYPO3\CMS\Core\Utility\GeneralUtility;
    use TYPO3\CMS\Core\Messaging\FlashMessage;
 
+   // FlashMessage($message, $title, $severity = self::OK, $storeInSession)
    $message = GeneralUtility::makeInstance(FlashMessage::class,
       'My message text',
       'Message Header',
       FlashMessage::WARNING,
       true
    );
 
-*  Line 5: The text of the message
-*  Line 6: [optional] the header
-*  Line 7: [optional] the severity defaults to FlashMessage::OK
-*  Line 8: [optional] whether the message should be stored in the session or
-   only in the \TYPO3\CMS\Core\Messaging\FlashMessageQueue object (default is false)
+:php:`$message:`
+   The text of the message
+:php:`$title:`
+   [optional] the header
+:php:`$severity:`
+   [optional] the severity (default: :php:`FlashMessage::OK`)
+:php:`$storeInSession:`
+   [optional] :php:`true`: store in the session or :php:`false`: store
+   only in the :php:`\TYPO3\CMS\Core\Messaging\FlashMessageQueue` object. Storage
+   in the session should be used if you need the message to be still present after
+   a redirection (default: :php:`false`).
 
 
 Flash messages severities
@@ -77,11 +84,6 @@ The severity is defined by using class constants provided by
 
 *  :php:`FlashMessage::ERROR` for errors
 
-The fourth parameter passed to the constructor is a flag that
-indicates whether the message should be stored in the session or not (the
-default is not). Storage in the session should be used if you need the
-message to be still present after a redirection.
-
 In backend modules you can then make that message appear on top of the
 module after a page refresh or the rendering of the next page request
 or render it on your own where ever you want.