Clean up settings subsequent pairing aconfig flag

BUG: 362649019
Test: atest FastPairDeviceGroupControllerTest
Flag: EXEMPT clean up
Change-Id: Ia49b0e4e9e5b9af7fe33b2182344f7a43786f111

aconfig/settings_connecteddevice_flag_declarations.aconfig

@@ -1,13 +1,6 @@
 package: "com.android.settings.flags"
 container: "system_ext"
 
-flag {
-  name: "enable_subsequent_pair_settings_integration"
-  namespace: "pixel_cross_device_control"
-  description: "Gates whether to enable subsequent pair Settings integration."
-  bug: "299405720"
-}
-
 flag {
   name: "rotation_connected_display_setting"
   namespace: "display_manager"
@@ -47,4 +40,4 @@ flag {
     metadata {
         purpose: PURPOSE_BUGFIX
     }
-}
+}