iOS: Remove QIOSKeyboardListener self-change assert/guard

We're fairly confident self won't change in that case, and the
assert was causing warnings in release builds.

Change-Id: I4a826579bb4cedef8423e8d43cb370e1f3b80407
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@theqtcompany.com>
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@theqtcompany.com>

src/plugins/platforms/ios/qiosinputcontext.mm

@@ -75,9 +75,7 @@ static QUIView *focusView()
 
 - (id)initWithQIOSInputContext:(QIOSInputContext *)context
 {
-    id originalSelf = self;
     if (self = [super initWithTarget:self action:@selector(gestureStateChanged:)]) {
-        Q_ASSERT(self == originalSelf);
 
         m_context = context;