Delete chrome::kAutoPasswordGenerationLearnMoreURL

It's not used anymore, last usage was removed
in https://codereview.chromium.org/583883003

R=gcasto@chromium.org

Review URL: https://codereview.chromium.org/877183003

Cr-Commit-Position: refs/heads/master@{#313560}

chrome/common/url_constants.cc

@@ -363,9 +363,6 @@ const char kExtensionResourceInvalidRequestURL[] =
 const char kSyncGoogleDashboardURL[] =
     "https://www.google.com/settings/chrome/sync/";
 
-const char kAutoPasswordGenerationLearnMoreURL[] =
-    "https://support.google.com/chrome/?p=ui_generate_password";
-
 const char kPasswordManagerLearnMoreURL[] =
 #if defined(OS_CHROMEOS)
     "https://support.google.com/chromeos/?p=settings_password";

chrome/common/url_constants.h

@@ -347,9 +347,6 @@ extern const char kExtensionResourceInvalidRequestURL[];
 
 extern const char kSyncGoogleDashboardURL[];
 
-// "Learn more" URL for the auto password generation.
-extern const char kAutoPasswordGenerationLearnMoreURL[];
-
 extern const char kPasswordManagerLearnMoreURL[];
 extern const char kPasswordManagerAccountDashboardURL[];