Don't let visibility bit get nuked when updating effects.

Fixes: lp:1836183
* https://bugs.launchpad.net/kicad/+bug/1836183

(cherry picked from commit 6c9e34e799)

pcbnew/dialogs/dialog_exchange_footprints.cpp

@@ -386,7 +386,12 @@ void processTextItem( const TEXTE_MODULE& aSrc, TEXTE_MODULE& aDest,
     }
 
     if( !resetTextEffects )
+    {
+        // Careful: the visible bit is also in Effects
+        bool visible = aDest.IsVisible();
         aDest.SetEffects( aSrc );
+        aDest.SetVisible( visible );
+    }
 }