widget explorer: Clarify the meaning of "uninstallable" using i18nc

Give context though i18nc for the use of "uninstallable" so that it won't be misinterpreted as "not installable" by translators, as has happened in some cases (e.g. sv & zh_TW).

components/shellprivate/widgetexplorer/widgetexplorer.cpp

@@ -115,7 +115,7 @@ void WidgetExplorerPrivate::initFilters()
                               KCategorizedItemsViewModels::Filter(QStringLiteral("running"), true),
                               QIcon::fromTheme(QStringLiteral("dialog-ok")));
 
-        filterModel.addFilter(i18n("Uninstallable"),
+        filterModel.addFilter(i18nc("@item:inmenu used in the widget filter. Filter widgets that can be un-installed from the system, which are usually installed by the user to a local place.", "Uninstallable"),
                               KCategorizedItemsViewModels::Filter(QStringLiteral("local"), true),
                               QIcon::fromTheme(QStringLiteral("edit-delete")));