Revert "[ios] Ensure proper shutdown of Chrome on iOS."

ios/chrome/app/main_controller.mm

Index: ios/chrome/app/main_controller.mm
diff --git a/ios/chrome/app/main_controller.mm b/ios/chrome/app/main_controller.mm
index 8d7a651ad25691f9199d54fa490b50284ad3cb33..f87bd91e45c3363e93d27a2599a623970f46b99c 100644
--- a/ios/chrome/app/main_controller.mm
+++ b/ios/chrome/app/main_controller.mm
@@ -680,7 +680,6 @@ enum class StackViewDismissalMode { NONE, NORMAL, INCOGNITO };
   // Initialize and set the main browser state.
   [self initializeBrowserState:chromeBrowserState];
   _mainBrowserState = chromeBrowserState;
-  [_browserViewWrangler shutdown];
   _browserViewWrangler =
       [[BrowserViewWrangler alloc] initWithBrowserState:_mainBrowserState
                                        tabModelObserver:self];
@@ -911,7 +910,6 @@ enum class StackViewDismissalMode { NONE, NORMAL, INCOGNITO };
   [_spotlightManager shutdown];
   _spotlightManager = nil;
 
-  [_browserViewWrangler shutdown];
   _browserViewWrangler = nil;
 
   _chromeMain.reset();
@@ -2553,7 +2551,6 @@ enum class StackViewDismissalMode { NONE, NORMAL, INCOGNITO };
   // Create a BrowserViewWrangler with a null browser state. This will trigger
   // assertions if the BrowserViewWrangler is asked to create any BVC or
   // tabModel objects, but it will accept assignments to them.
-  [_browserViewWrangler shutdown];
   _browserViewWrangler =
       [[BrowserViewWrangler alloc] initWithBrowserState:nullptr
                                        tabModelObserver:self];