chrome/browser/ui/webauthn: remove Continue button from account selector

The accounts themselves are clickable but, previously, there was also a
continue button that happened to select the first account. Since I'm not
sure what the behaviour of such a button should be, this change removes
it.

Change-Id: I7977606119b9b44a8134ca11c868c95153e13ff7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1592372
Commit-Queue: Adam Langley <agl@chromium.org>
Commit-Queue: Nina Satragno <nsatragno@chromium.org>
Auto-Submit: Adam Langley <agl@chromium.org>
Reviewed-by: Nina Satragno <nsatragno@chromium.org>
Cr-Commit-Position: refs/heads/master@{#655700}

chrome/browser/ui/webauthn/sheet_models.cc

@@ -1028,11 +1028,11 @@ base::string16 AuthenticatorSelectAccountSheetModel::GetStepDescription()
 }
 
 bool AuthenticatorSelectAccountSheetModel::IsAcceptButtonVisible() const {
-  return true;
+  return false;
 }
 
 bool AuthenticatorSelectAccountSheetModel::IsAcceptButtonEnabled() const {
-  return true;
+  return false;
 }
 
 base::string16 AuthenticatorSelectAccountSheetModel::GetAcceptButtonLabel()