kcms/decoration: use sentence case for combobox

The HIG recommend sentence case for combobox entries. The window border
combobox in the decoration kcm currently uses title case, except for the
option following the theme default, which uses mixed title and sentence
case.

This change converts the labels to sentence case. The "Theme's default"
option is also renamed to "Theme default", as this is a shorter and more
common construction in UI strings.

src/kcms/decoration/kcm.cpp

@@ -174,7 +174,7 @@ QStringList KCMKWinDecoration::borderSizesModel() const
     // Use index 0 for borderSizeAuto == true
     // The rest of indexes get offset by 1
     QStringList model = Utils::getBorderSizeNames().values();
-    model.insert(0, i18nc("%1 is the name of a border size", "Theme's default (%1)", model.at(recommendedBorderSize())));
+    model.insert(0, i18nc("%1 is the name of a border size", "Theme default (%1)", model.at(recommendedBorderSize())));
     return model;
 }
 

src/kcms/decoration/utils.cpp

@@ -22,15 +22,15 @@ const QMap<QString, KDecoration2::BorderSize> s_borderSizes{
     {QStringLiteral("VeryHuge"), KDecoration2::BorderSize::VeryHuge},
     {QStringLiteral("Oversized"), KDecoration2::BorderSize::Oversized}};
 const QMap<KDecoration2::BorderSize, QString> s_borderSizeNames{
-    {KDecoration2::BorderSize::None, i18n("No Window Borders")},
-    {KDecoration2::BorderSize::NoSides, i18n("No Side Window Borders")},
-    {KDecoration2::BorderSize::Tiny, i18n("Tiny Window Borders")},
-    {KDecoration2::BorderSize::Normal, i18n("Normal Window Borders")},
-    {KDecoration2::BorderSize::Large, i18n("Large Window Borders")},
-    {KDecoration2::BorderSize::VeryLarge, i18n("Very Large Window Borders")},
-    {KDecoration2::BorderSize::Huge, i18n("Huge Window Borders")},
-    {KDecoration2::BorderSize::VeryHuge, i18n("Very Huge Window Borders")},
-    {KDecoration2::BorderSize::Oversized, i18n("Oversized Window Borders")}};
+    {KDecoration2::BorderSize::None, i18n("No window borders")},
+    {KDecoration2::BorderSize::NoSides, i18n("No side window borders")},
+    {KDecoration2::BorderSize::Tiny, i18n("Tiny window borders")},
+    {KDecoration2::BorderSize::Normal, i18n("Normal window borders")},
+    {KDecoration2::BorderSize::Large, i18n("Large window borders")},
+    {KDecoration2::BorderSize::VeryLarge, i18n("Very large window borders")},
+    {KDecoration2::BorderSize::Huge, i18n("Huge window borders")},
+    {KDecoration2::BorderSize::VeryHuge, i18n("Very huge window borders")},
+    {KDecoration2::BorderSize::Oversized, i18n("Oversized window borders")}};
 
 const QHash<KDecoration2::DecorationButtonType, QChar> s_buttonNames{
     {KDecoration2::DecorationButtonType::Menu, QChar('M')},