Apply suggestions from code review

Co-authored-by: Daniel Schürmann <daschuer@mixxx.org>

Author: JoergAtGithub

src/engine/sync/abletonlink.cpp

@@ -53,14 +53,6 @@ AbletonLink::~AbletonLink() {
     m_pLink->setNumPeersCallback([](std::size_t) {});
     m_pLink->enable(false);
 
-    // Disconnect the connection from the Link GUI button
-    if (m_pLinkButton) {
-        QObject::disconnect(m_pLinkButton.get(),
-                &ControlObject::valueChanged,
-                this,
-                &AbletonLink::slotControlSyncEnabled);
-    }
-
     // Destroy control objects before releasing Link.
     m_pNumLinkPeers.reset();
     m_pLinkButton.reset();

src/engine/sync/abletonlink.h

@@ -103,7 +103,7 @@ class AbletonLink : public QObject, public Syncable {
   private:
     ableton::link::HostTimeFilter<MixxxClockRef> m_hostTimeFilter;
     QString m_group;
-    EngineSync* m_pEngineSync; // unowned, must outlive this.
+    EngineSync* m_pEngineSync; // borrowed, must outlive this.
     SyncMode m_syncMode;
 
     mixxx::Bpm m_oldTempo;