ImageViewer: Inline imageviewertoolbar.ui

Change-Id: Ie7b4c77477ce78107c5f55edccdcbd4db74b010b
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>
Reviewed-by: Eike Ziller <eike.ziller@qt.io>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>

src/plugins/imageviewer/imageviewer.h

@@ -37,8 +37,8 @@ class QAbstractButton;
 class QAction;
 QT_END_NAMESPACE
 
-namespace ImageViewer {
-namespace Internal {
+namespace ImageViewer::Internal {
+
 class ImageViewerFile;
 
 class ImageViewer : public Core::IEditor
@@ -78,5 +78,4 @@ private:
     struct ImageViewerPrivate *d;
 };
 
-} // namespace Internal
-} // namespace ImageViewer
+} // ImageViewer::Internal