Don't warn when loading icons via the image loaders

9d5ae9f26c98 introduced a warning when a matching icon engine was not
found for a given file suffix, under the assumption that all formats
would go through icon engine plugins. Unfortunately QIcon itself falls
back to a direct use of QPixmapIconEngine when no icon engine plugin
is found, which would lead to the warning being emitted for built in
formats such as PNG.

Until this code can be moved properly into QPixmapIconEngine we'll
remove it.

Change-Id: I14d1d33a0f0c29e4b4604ef3b53c05cb8e02f867
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

src/gui/image/qicon.cpp

@@ -1049,8 +1049,6 @@ static QIconEngine *iconEngineFromSuffix(const QString &fileName, const QString
             }
         }
     }
-    qWarning("Could not find icon engine for suffix '%s' of file '%s'",
-        qUtf8Printable(suffix), qUtf8Printable(fileName));
     return nullptr;
 }