[Payments] Add an entry for Payment Request to chrome://flags on iOS

ios/chrome/browser/experimental_flags.mm

Index: ios/chrome/browser/experimental_flags.mm
diff --git a/ios/chrome/browser/experimental_flags.mm b/ios/chrome/browser/experimental_flags.mm
index 3e55afffe705303bde742af6e5a6d4b7625518ff..b904c366e009016e299b8cbf8e3f3f03de0fb2ce 100644
--- a/ios/chrome/browser/experimental_flags.mm
+++ b/ios/chrome/browser/experimental_flags.mm
@@ -172,25 +172,6 @@ bool IsPasswordGenerationEnabled() {
   return group_name != "Disabled";
 }
 
-bool IsPaymentRequestEnabled() {
-  // This call activates the field trial, if needed, so it must come before any
-  // early returns.
-  std::string group_name =
-      base::FieldTrialList::FindFullName("IOSPaymentRequest");
-
-  // Check if the experimental flag is forced on or off.
-  base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
-  if (command_line->HasSwitch(switches::kEnablePaymentRequest)) {
-    return true;
-  } else if (command_line->HasSwitch(switches::kDisablePaymentRequest)) {
-    return false;
-  }
-
-  // Check if the Finch experiment is turned on.
-  return base::StartsWith(group_name, "Enabled",
-                          base::CompareCase::INSENSITIVE_ASCII);
-}
-
 bool IsPhysicalWebEnabled() {
   base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
   if (command_line->HasSwitch(switches::kEnableIOSPhysicalWeb)) {