Nuke kQuickUnlockPinSignin feature

The feature is not used at all.

Bug: none
Change-Id: I9ecbed46b513ce7b1dff4ddbfc45f4741af4209a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2362813
Commit-Queue: Roman Sorokin [CET] <rsorokin@chromium.org>
Commit-Queue: Renato Silva <rrsilva@google.com>
Auto-Submit: Roman Sorokin [CET] <rsorokin@chromium.org>
Reviewed-by: Renato Silva <rrsilva@google.com>
Cr-Commit-Position: refs/heads/master@{#799137}

chrome/common/chrome_features.cc

@@ -636,10 +636,6 @@ const base::Feature kQuickUnlockPinAutosubmit{
 // Controls whether the PIN auto submit backfill operation should be performed.
 const base::Feature kQuickUnlockPinAutosubmitBackfill{
     "QuickUnlockPinAutosubmitBackfill", base::FEATURE_ENABLED_BY_DEFAULT};
-
-// Enables pin on the login screen.
-const base::Feature kQuickUnlockPinSignin{"QuickUnlockPinSignin",
-                                          base::FEATURE_DISABLED_BY_DEFAULT};
 #endif
 
 // Enables using quiet prompts for notification permission requests.

chrome/common/chrome_features.h

@@ -419,9 +419,6 @@ extern const base::Feature kQuickUnlockPinAutosubmit;
 // users have their preferences backfilled.
 COMPONENT_EXPORT(CHROME_FEATURES)
 extern const base::Feature kQuickUnlockPinAutosubmitBackfill;
-
-COMPONENT_EXPORT(CHROME_FEATURES)
-extern const base::Feature kQuickUnlockPinSignin;
 #endif
 
 COMPONENT_EXPORT(CHROME_FEATURES)