[ios] Remove obsolete overload of InitializeFirebase

Downstream code has been converted to overload the version of the
method taking base::Time parameter. Remove old int64_t version of
the method.

Bug: none
Change-Id: I744fb0c345aeec963c2ca1f8010713a591680271
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2245909
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#779250}

ios/public/provider/chrome/browser/distribution/app_distribution_provider.h

@@ -37,7 +37,6 @@ class AppDistributionProvider {
   // is used to detect "legacy" users that installed Chrome before Firebase
   // was integrated and thus should not have Firebase enabled.
   virtual void InitializeFirebase(base::Time install_date, bool is_first_run);
-  virtual void InitializeFirebase(int64_t install_date, bool is_first_run);
 };
 
 #endif  // IOS_PUBLIC_PROVIDER_CHROME_BROWSER_DISTRIBUTION_APP_DISTRIBUTION_PROVIDER_H_

ios/public/provider/chrome/browser/distribution/app_distribution_provider.mm

@@ -23,12 +23,4 @@ void AppDistributionProvider::ScheduleDistributionNotifications(
 void AppDistributionProvider::CancelDistributionNotifications() {}
 
 void AppDistributionProvider::InitializeFirebase(base::Time install_date,
-                                                 bool is_first_run) {
-  // Call int64_t version since it is the only one implemented downstream.
-  // Will remove this once downstream has been fixed to overload the
-  // base::Time version of the function.
-  InitializeFirebase(install_date.ToTimeT(), is_first_run);
-}
-
-void AppDistributionProvider::InitializeFirebase(int64_t install_date,
                                                  bool is_first_run) {}