Remove some redundant addWorkspaceRepaint() calls

These repaints were added to fix visual artifacts that appear when
shadow is removed, but since items schedule repaints when needed, we can
remove these two.

src/abstract_client.cpp

@@ -234,7 +234,6 @@ void AbstractClient::markAsZombie()
 {
     Q_ASSERT(!m_zombie);
     m_zombie = true;
-    addWorkspaceRepaint(visibleGeometry());
 }
 
 Layer AbstractClient::layer() const

src/unmanaged.cpp

@@ -131,7 +131,6 @@ bool Unmanaged::track(xcb_window_t w)
 
 void Unmanaged::release(ReleaseReason releaseReason)
 {
-    addWorkspaceRepaint(visibleGeometry());
     Deleted* del = nullptr;
     if (releaseReason != ReleaseReason::KWinShutsDown) {
         del = Deleted::create(this);