Fix rate limiting settings observer

The obvserver accidentally observed Settings.Secure instad of
Settings.Global.

Test: atest CtsNetTestCases:RateLimitTest
Bug: 218840346
Change-Id: If5ade0c0e269c01b76428d5635d0913330d7015e
diff --git a/service/src/com/android/server/ConnectivityService.java b/service/src/com/android/server/ConnectivityService.java
index 6024a2a..d6ef6df 100644
--- a/service/src/com/android/server/ConnectivityService.java
+++ b/service/src/com/android/server/ConnectivityService.java
@@ -1752,7 +1752,7 @@
 
         // Watch for ingress rate limit changes.
         mSettingsObserver.observe(
-                Settings.Secure.getUriFor(
+                Settings.Global.getUriFor(
                         ConnectivitySettingsManager.INGRESS_RATE_LIMIT_BYTES_PER_SECOND),
                 EVENT_INGRESS_RATE_LIMIT_CHANGED);
     }