[PR] Removes unused lambda capture breaking XCode 9.3

Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: I723f6632b3708f86e25158f4065cb5d70590ffe6
Reviewed-on: https://chromium-review.googlesource.com/1010463Reviewed-by: Justin Cohen <justincohen@chromium.org>
Commit-Queue: Moe Ahmadi <mahmadi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550350}

ios/chrome/browser/payments/payment_request.mm

@@ -551,7 +551,7 @@ void PaymentRequest::PopulatePaymentMethodCache(
 
   const auto first_complete_payment_method =
       std::find_if(payment_methods_.begin(), payment_methods_.end(),
-                   [this](PaymentInstrument* payment_method) {
+                   [](PaymentInstrument* payment_method) {
                      return payment_method->IsCompleteForPayment() &&
                             payment_method->IsExactlyMatchingMerchantRequest();
                    });