Update learn more link for APP download warnings

The current link goes to a generic APP FAQ, but we can link to the specific
section related to Advanced Protection download warnings.

This fixes b/153866355

Change-Id: I449e4d627fb70ac295fa6937a40c89a1e3879bfa
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2250824
Auto-Submit: Daniel Rubery <drubery@chromium.org>
Reviewed-by: Xinghui Lu <xinghuilu@chromium.org>
Commit-Queue: Xinghui Lu <xinghuilu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#779581}

chrome/common/url_constants.cc

@@ -16,7 +16,7 @@ const char kAutomaticSettingsResetLearnMoreURL[] =
     "https://support.google.com/chrome/?p=ui_automatic_settings_reset";
 
 const char kAdvancedProtectionDownloadLearnMoreURL[] =
-    "https://support.google.com/accounts/?p=ap_faq";
+    "https://support.google.com/accounts/accounts?p=safe-browsing";
 
 const char kBluetoothAdapterOffHelpURL[] =
     "https://support.google.com/chrome?p=bluetooth";