get back the plugin manager svg icon again, removed mistakenly by 9138ba3

Author: slarosa

src/app/qgisapp.cpp

@@ -1711,7 +1711,7 @@ void QgisApp::setTheme( QString theThemeName )
   mActionRemoveAllFromOverview->setIcon( QgsApplication::getThemeIcon( "/mActionRemoveAllFromOverview.svg" ) );
   mActionToggleFullScreen->setIcon( QgsApplication::getThemeIcon( "/mActionToggleFullScreen.png" ) );
   mActionProjectProperties->setIcon( QgsApplication::getThemeIcon( "/mActionProjectProperties.png" ) );
-  mActionManagePlugins->setIcon( QgsApplication::getThemeIcon( "/mActionShowPluginManager.png" ) );
+  mActionManagePlugins->setIcon( QgsApplication::getThemeIcon( "/mActionShowPluginManager.svg" ) );
   mActionShowPythonDialog->setIcon( QgsApplication::getThemeIcon( "console/iconRunConsole.png" ) );
   mActionCheckQgisVersion->setIcon( QgsApplication::getThemeIcon( "/mActionCheckQgisVersion.png" ) );
   mActionOptions->setIcon( QgsApplication::getThemeIcon( "/mActionOptions.svg" ) );