speculative fix to main vc related crash (#2864)

Task/Issue URL: https://app.asana.com/0/392891325557410/1207313758905436/f
Tech Design URL:
CC:

Description:
Be less aggressive about forcing view layout update and ask nicely for constraints to be updated at the next opportunity.

DuckDuckGo/MainViewController.swift

@@ -1602,12 +1602,11 @@ extension MainViewController: BrowserChromeDelegate {
         let updateBlock = {
             self.updateToolbarConstant(percent)
             self.updateNavBarConstant(percent)
+            self.view.needsUpdateConstraints()
 
             self.viewCoordinator.navigationBarContainer.alpha = percent
             self.viewCoordinator.tabBarContainer.alpha = percent
             self.viewCoordinator.toolbar.alpha = percent
-
-            self.view.layoutIfNeeded()
         }
 
         if animated {