Clean up unused metrics flag. Logic is in blimp browser instead.

chrome/browser/browser_process_impl.cc

Index: chrome/browser/browser_process_impl.cc
diff --git a/chrome/browser/browser_process_impl.cc b/chrome/browser/browser_process_impl.cc
index b2f8f7272b9c85b201b14b384bdb9e494e6a0c09..75173b3b692cd0f24dce67489ece96ab3c233362 100644
--- a/chrome/browser/browser_process_impl.cc
+++ b/chrome/browser/browser_process_impl.cc
@@ -803,14 +803,8 @@ void BrowserProcessImpl::RegisterPrefs(PrefRegistrySimple* registry) {
                                std::string());
 #endif  // defined(OS_CHROMEOS)
 
-#if defined(ENABLE_REPORTING_BLIMP)
-  // Enables reporting for the (headless) blimp engine. Defined in
-  // components/metrics/BUILD.gn
-  registry->RegisterBooleanPref(metrics::prefs::kMetricsReportingEnabled, true);
-#else
   registry->RegisterBooleanPref(metrics::prefs::kMetricsReportingEnabled,
                                 GoogleUpdateSettings::GetCollectStatsConsent());
-#endif // defined(ENABLE_REPORTING_HEADLESS)
 
 #if BUILDFLAG(ANDROID_JAVA_UI)
   registry->RegisterBooleanPref(