[Autofill] Remove AutofillUpstreamSendPanFirstSix feature flag

Usage was removed in
https://chromium-review.googlesource.com/c/chromium/src/+/1188587 but
the actual feature flag was missed.  This is final cleanup.

Change-Id: I84537c6112eea803a991eefff9c997c7f0dce758
Reviewed-on: https://chromium-review.googlesource.com/1213923
Commit-Queue: Mathieu Perreault <mathp@chromium.org>
Reviewed-by: Mathieu Perreault <mathp@chromium.org>
Cr-Commit-Position: refs/heads/master@{#590172}

components/autofill/core/common/autofill_features.cc

@@ -239,9 +239,6 @@ const base::Feature kAutofillUpstreamEditableCardholderName{
     "AutofillUpstreamEditableCardholderName",
     base::FEATURE_DISABLED_BY_DEFAULT};
 
-const base::Feature kAutofillUpstreamSendPanFirstSix{
-    "AutofillUpstreamSendPanFirstSix", base::FEATURE_DISABLED_BY_DEFAULT};
-
 const base::Feature kAutofillUpstreamUpdatePromptExplanation{
     "AutofillUpstreamUpdatePromptExplanation",
     base::FEATURE_ENABLED_BY_DEFAULT};
@@ -335,10 +332,6 @@ bool IsAutofillUpstreamEditableCardholderNameExperimentEnabled() {
   return base::FeatureList::IsEnabled(kAutofillUpstreamEditableCardholderName);
 }
 
-bool IsAutofillUpstreamSendPanFirstSixExperimentEnabled() {
-  return base::FeatureList::IsEnabled(kAutofillUpstreamSendPanFirstSix);
-}
-
 bool IsAutofillUpstreamUpdatePromptExplanationExperimentEnabled() {
   return base::FeatureList::IsEnabled(kAutofillUpstreamUpdatePromptExplanation);
 }

components/autofill/core/common/autofill_features.h

@@ -69,7 +69,6 @@ extern const base::Feature kAutofillUpstreamBlankCardholderNameField;
 extern const base::Feature kAutofillUpstreamDisallowElo;
 extern const base::Feature kAutofillUpstreamDisallowJcb;
 extern const base::Feature kAutofillUpstreamEditableCardholderName;
-extern const base::Feature kAutofillUpstreamSendPanFirstSix;
 extern const base::Feature kAutofillUpstreamUpdatePromptExplanation;
 extern const base::Feature kAutofillUpstreamUseGooglePayBrandingOnMobile;
 extern const base::Feature kAutofillUsePaymentsCustomerData;
@@ -136,11 +135,6 @@ bool IsAutofillUpstreamBlankCardholderNameFieldExperimentEnabled();
 // NOT a Google Payments customer.
 bool IsAutofillUpstreamEditableCardholderNameExperimentEnabled();
 
-// Returns whether the experiment is enabled where Chrome Upstream sends the
-// first six digits of the card PAN to Google Payments to help determine whether
-// card upload is possible.
-bool IsAutofillUpstreamSendPanFirstSixExperimentEnabled();
-
 // Returns whether the experiment is enbabled where upstream sends updated
 // prompt explanation which changes 'save this card' to 'save your card and
 // billing address.'