Do not use "gtk3" key to avoid conflict with QGtkStyle from Qt upstream (#150)

Author: grulja

src/decoration/decorationplugin.cpp

@@ -23,7 +23,7 @@
 QWaylandAbstractDecoration *QGnomePlatformDecorationPlugin::create(const QString &key, const QStringList &paramList)
 {
     Q_UNUSED(paramList)
-    if (key == "gnome" || key == "gtk3" || key == "qgnomeplatform")
+    if (key == "gnome" || key == "qgnomeplatform")
         return new QGnomePlatformDecoration();
     return nullptr;
 }

src/decoration/qgnomeplatformdecoration.json

@@ -1,3 +1,3 @@
 {
-    "Keys": [ "gnome", "gtk3", "qgnomeplatform" ]
+    "Keys": [ "gnome", "qgnomeplatform" ]
 }

src/theme/platformplugin.cpp

@@ -27,7 +27,7 @@ QGnomePlatformThemePlugin::QGnomePlatformThemePlugin(QObject *parent)
 QPlatformTheme *QGnomePlatformThemePlugin::create(const QString &key, const QStringList &paramList)
 {
     Q_UNUSED(paramList)
-    if (key == "gnome" || key == "gtk3" || key == "qgnomeplatform")
+    if (key == "gnome" || key == "qgnomeplatform")
         return new QGnomePlatformTheme();
     return nullptr;
 }

src/theme/qgnomeplatformtheme.json

@@ -1,3 +1,3 @@
 {
-    "Keys": [ "gnome", "gtk3", "qgnomeplatform" ]
+    "Keys": [ "gnome", "qgnomeplatform" ]
 }