Revert "Re-enabled Space for toggling layer visibility"

This reverts commit 0de0f20.

This shortcut was only provided for backwards compatibility, but it
often conflicts with using Space for panning the map view and since
359dcb9 there are global shortcuts
available for toggling layer visility and locked status, making this
shortcut no longer necessary.

See issue mapeditor#3672.

src/tiled/layerdock.cpp

@@ -24,7 +24,6 @@
 #include "layerdock.h"
 
 #include "actionmanager.h"
-#include "changelayer.h"
 #include "layer.h"
 #include "layermodel.h"
 #include "map.h"
@@ -478,8 +477,6 @@ void LayerView::contextMenuEvent(QContextMenuEvent *event)
 
 void LayerView::keyPressEvent(QKeyEvent *event)
 {
-    Layer *layer = mMapDocument ? mMapDocument->currentLayer() : nullptr;
-
     switch (event->key()) {
     case Qt::Key_Delete:
     case Qt::Key_Backspace:
@@ -488,17 +485,6 @@ void LayerView::keyPressEvent(QKeyEvent *event)
             return;
         }
         break;
-    case Qt::Key_Space:
-        if (layer) {
-            QUndoCommand *command = nullptr;
-            if (event->modifiers() & Qt::ControlModifier)
-                command = new SetLayerLocked(mMapDocument, { layer }, !layer->isLocked());
-            else
-                command = new SetLayerVisible(mMapDocument, { layer }, !layer->isVisible());
-            mMapDocument->undoStack()->push(command);
-            return;
-        }
-        break;
     }
 
     QTreeView::keyPressEvent(event);