Infrastructure: update dates for 2024 (Mudlet#7274)

#### Brief overview of PR changes/additions
Update the second year in the date range shown in copyright lines for
Mudlet itself.

#### Motivation for adding to Mudlet
It is June already and it hadn't been done by anyone!

#### Other info (issues closed, discussion etc)
Same change is also needed in the installers repository:
Mudlet/installers#116

Signed-off-by: Stephen Lyons <slysven@virginmedia.com>

src/dlgAboutDialog.cpp

@@ -84,7 +84,7 @@ dlgAboutDialog::dlgAboutDialog(QWidget* parent)
 
         // Repeat for other text, but we know it will fit at given size
         // PLACEMARKER: Date-stamp needing annual update
-        QString sourceCopyrightText = qsl("©️ Mudlet makers 2008-2023");
+        QString sourceCopyrightText = qsl("©️ Mudlet makers 2008-2024");
         QFont font(qsl("Bitstream Vera Serif"), 16, QFont::Bold | QFont::Serif | QFont::PreferMatch | QFont::PreferAntialias);
         QTextLayout copyrightTextLayout(sourceCopyrightText, font, painter.device());
         copyrightTextLayout.beginLayout();

src/main.cpp

@@ -379,7 +379,7 @@ int main(int argc, char* argv[])
         texts << appendLF.arg(QCoreApplication::translate("main", "Qt libraries %1 (compilation) %2 (runtime)",
              "%1 and %2 are version numbers").arg(QLatin1String(QT_VERSION_STR), qVersion()));
         // PLACEMARKER: Date-stamp needing annual update
-        texts << appendLF.arg(QCoreApplication::translate("main", "Copyright © 2008-2023  Mudlet developers"));
+        texts << appendLF.arg(QCoreApplication::translate("main", "Copyright © 2008-2024  Mudlet developers"));
         texts << appendLF.arg(QCoreApplication::translate("main", "Licence GPLv2+: GNU GPL version 2 or later - http://gnu.org/licenses/gpl.html"));
         texts << appendLF.arg(QCoreApplication::translate("main", "This is free software: you are free to change and redistribute it.\n"
                                                                   "There is NO WARRANTY, to the extent permitted by law."));
@@ -473,7 +473,7 @@ int main(int argc, char* argv[])
 
         // Repeat for other text, but we know it will fit at given size
         // PLACEMARKER: Date-stamp needing annual update
-        const QString sourceCopyrightText = qsl("©️ Mudlet makers 2008-2023");
+        const QString sourceCopyrightText = qsl("©️ Mudlet makers 2008-2024");
         const QFont font(qsl("Bitstream Vera Serif"), 16, QFont::Bold | QFont::Serif | QFont::PreferMatch | QFont::PreferAntialias);
         QTextLayout copyrightTextLayout(sourceCopyrightText, font, painter.device());
         copyrightTextLayout.beginLayout();