Doc: use [since] tag for enum values added in Qt 6.6

Remove the manual "This enum value has been introduced..." text. Doing
that only for 6.6 to avoid unnecessary cherry-pick conflicts and general
code churn.

Change-Id: I89a6fd313582fd0c5d6209608a3740f19f91bd01
Reviewed-by: Jan Arve Sæther <jan-arve.saether@qt.io>

src/corelib/text/qregularexpression.cpp

@@ -1857,9 +1857,8 @@ QString QRegularExpression::escape(QStringView str)
         The conversion will not anchor the pattern. This allows for partial string matches of
         wildcard expressions.
 
-    \value NonPathWildcardConversion
+    \value [since 6.6] NonPathWildcardConversion
         The conversion will \e{not} interpret the pattern as filepath globbing.
-        This enum value has been introduced in Qt 6.6.
 
     \sa QRegularExpression::wildcardToRegularExpression
 */

src/gui/kernel/qpalette.cpp

@@ -548,12 +548,12 @@ static void qt_palette_from_color(QPalette &pal, const QColor &button)
                        item. By default, the highlight color is
                        Qt::darkBlue.
 
-    \value AccentColor A color that typically contrasts or compliments
+    \value [since 6.6] AccentColor
+                       A color that typically contrasts or compliments
                        Base, Window and Button colors. It usually represents
                        the users' choice of desktop personalisation.
                        Styling of interactive components is a typical use case.
                        Unless explicitly set, it defaults to Highlight.
-                       This enum value has been introduced in Qt 6.6.
 
     \value HighlightedText  A text color that contrasts with \c Highlight.
                             By default, the highlighted text color is Qt::white.

src/gui/text/qtextformat.cpp

@@ -684,8 +684,8 @@ Q_GUI_EXPORT QDataStream &operator>>(QDataStream &stream, QTextTableCellFormat &
                             numeric lists.
     \value ListNumberSuffix Defines the text which is appended to item numbers in
                             numeric lists.
-    \value ListStart        Defines the first value of a list.
-                            This enum value has been added in Qt 6.6.
+    \value [since 6.6] ListStart
+                            Defines the first value of a list.
 
     Table and frame properties
 

src/widgets/styles/qstyleoption.cpp

@@ -1314,8 +1314,7 @@ QStyleOptionTab::QStyleOptionTab(int version)
     \value Middle The tab is neither the first nor the last tab in the tab bar.
     \value End The tab is the last tab in the tab bar.
     \value OnlyOneTab The tab is both the first and the last tab in the tab bar.
-    \value Moving The tab is moving by mouse drag or animation.
-           This enum value was added in Qt 6.6.
+    \value [since 6.6] Moving The tab is moving by mouse drag or animation.
 
     \sa position
 */