[ios] Roll ios/third_party/earl_grey to 451b6497352d0731e9827a338f32024e564078c6

Adds two fixes for Xcode 10 / iOS 12.

Bug: 843236
Change-Id: If619d0899e65fd86cf98a980dd0e6b741a4f5d90
Reviewed-on: https://chromium-review.googlesource.com/1142601Reviewed-by: Rohit Rao <rohitrao@chromium.org>
Commit-Queue: Justin Cohen <justincohen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576480}

DEPS

@@ -252,7 +252,7 @@ deps = {
     Var('chromium_git') + '/external/github.com/immersive-web/webxr-samples.git' + '@' + 'cf02f19c4ff6894705a9407722ab52551e010c60',
 
   'src/ios/third_party/earl_grey/src': {
-      'url': Var('chromium_git') + '/external/github.com/google/EarlGrey.git' + '@' + '91c27bb8a15e723df974f620f7f576a30a6a7484',
+      'url': Var('chromium_git') + '/external/github.com/google/EarlGrey.git' + '@' + '451b6497352d0731e9827a338f32024e564078c6',
       'condition': 'checkout_ios',
   },