[libcalamares] Drop unused parameter

- the `parent` when installing a translator was not used, so drop it
  from the API. Chase some uses of the API, but leave welcome-modules
   broken: there's a merge of those coming.

src/calamares/CalamaresApplication.cpp

@@ -83,7 +83,7 @@ CalamaresApplication::init()
     initQmlPath();
     initBranding();
 
-    CalamaresUtils::installTranslator( QLocale::system(), QString(), this );
+    CalamaresUtils::installTranslator( QLocale::system(), QString() );
 
     setQuitOnLastWindowClosed( false );
     setWindowIcon( QIcon( Calamares::Branding::instance()->imagePath( Calamares::Branding::ProductIcon ) ) );

src/libcalamares/utils/Retranslator.cpp

@@ -197,7 +197,7 @@ static QTranslator* s_tztranslator = nullptr;
 static QString s_translatorLocaleName;
 
 void
-installTranslator( const QLocale& locale, const QString& brandingTranslationsPrefix, QObject* )
+installTranslator( const QLocale& locale, const QString& brandingTranslationsPrefix )
 {
     loadSingletonTranslator( BrandingLoader( locale, brandingTranslationsPrefix ), s_brandingTranslator );
     loadSingletonTranslator( TZLoader( locale ), s_tztranslator );

src/libcalamares/utils/Retranslator.h

@@ -36,9 +36,8 @@ namespace CalamaresUtils
  * @brief installTranslator changes the application language.
  * @param locale the new locale.
  * @param brandingTranslationsPrefix the branding path prefix, from Calamares::Branding.
- * @param parent the parent QObject.
  */
-DLLEXPORT void installTranslator( const QLocale& locale, const QString& brandingTranslationsPrefix, QObject* parent );
+DLLEXPORT void installTranslator( const QLocale& locale, const QString& brandingTranslationsPrefix );
 
 DLLEXPORT QString translatorLocaleName();