i18n: simplify Label handling of sr@latin

src/libcalamares/locale/Label.cpp

@@ -56,15 +56,15 @@ Label::getLocale( const QString& localeName )
     {
         return QLocale();
     }
-    if ( localeName.contains( "@latin" ) )
+
+    // Special cases
+    if ( localeName == QStringLiteral( "sr@latin" ) )
     {
         QLocale loc( localeName );  // Ignores @latin
         return QLocale( loc.language(), QLocale::Script::LatinScript, loc.country() );
     }
-    else
-    {
-        return QLocale( localeName );
-    }
+
+    return QLocale( localeName );
 }
 
 }  // namespace Locale

src/libcalamares/locale/Label.h

@@ -86,8 +86,9 @@ public:
 
     /** @brief Get a Qt locale for the given @p localeName
      *
-     * This special-cases `sr@latin`, which is used as a translation
-     * name in Calamares, while Qt recognizes `sr@latn`.
+     * This handles special-cases in Calamares translations:
+     * - `sr@latin` is the name which Qt recognizes as `sr@latn`,
+     *   Serbian written with Latin characters (not Cyrillic).
      */
     static QLocale getLocale( const QString& localeName );