Don't add quotes for LaunchExternal in 3.0 either

The quotes do not work in GTK 3.0.5.  Since GTK is the only platform we
have left running 3.0, we can remove this.

common/launch_ext.cpp

@@ -29,14 +29,6 @@ void LaunchExternal( const wxString& aPath )
 #else
     wxString path( aPath );
 
-#if !wxCHECK_VERSION( 3, 1, 0 )
-    // Quote in case there are spaces in the path.
-    // Not needed on 3.1.4, but needed in 3.0 versions
-    // Moreover, on Linux, on 3.1.4 wx version, adding quotes breaks
-    // wxLaunchDefaultApplication
-    QuoteString( path );
-#endif
-
     wxLaunchDefaultApplication( path );
 #endif
 }