[ios] Calls dismissInfobarModal on right object for Translate Infobar Modal.

https://crrev.com/c/1996167 introduced a refactoring to infobar_translate_vc
that broke this functionality, this CL fixes that by making the call to
the right object.

Bug: 1043094
Change-Id: I4ba6f804f91697c24264fec09584acd1c7a32a16
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2015801
Commit-Queue: Chris Lu <thegreenfrog@chromium.org>
Auto-Submit: Sergio Collazos <sczs@chromium.org>
Reviewed-by: Chris Lu <thegreenfrog@chromium.org>
Cr-Commit-Position: refs/heads/master@{#734509}

ios/chrome/browser/ui/infobars/modals/infobar_translate_table_view_controller.mm

@@ -91,7 +91,7 @@ typedef NS_ENUM(NSInteger, ItemType) {
   // Configure the NavigationBar.
   UIBarButtonItem* cancelButton = [[UIBarButtonItem alloc]
       initWithBarButtonSystemItem:UIBarButtonSystemItemCancel
-                           target:self.infobarModalDelegate
+                           target:self
                            action:@selector(dismissInfobarModal)];
   cancelButton.accessibilityIdentifier = kInfobarModalCancelButton;
   self.navigationItem.leftBarButtonItem = cancelButton;