Disable supervised user creation when force sign in is enabled.

chrome/browser/BUILD.gn

Index: chrome/browser/BUILD.gn
diff --git a/chrome/browser/BUILD.gn b/chrome/browser/BUILD.gn
index 24a4e337bbbfcc0fe93cd5f3c142858ef17c625c..52453d74667098ff276fa086f798158aae87af99 100644
--- a/chrome/browser/BUILD.gn
+++ b/chrome/browser/BUILD.gn
@@ -3701,6 +3701,12 @@ split_static_library("browser") {
       "supervised_user/supervised_user_theme.h",
     ]
   }
+  if (enable_supervised_users && !is_android && !is_chromeos) {
+    sources += [
+      "supervised_user/supervised_user_creation_policy_handler.cc",
+      "supervised_user/supervised_user_creation_policy_handler.h",
+    ]
+  }
   if (enable_webrtc) {
     sources += [
       "media/audio_debug_recordings_handler.h",