Add metricsEvent for WifiCallingSettingsForSub fragment.

Bug: 65648147
Test: Manual

Change-Id: I2447a809e5ab619cac30fc56ed38f8fb3853b317
diff --git a/proto/src/metrics_constants.proto b/proto/src/metrics_constants.proto
index 8e88359..a13be0b 100644
--- a/proto/src/metrics_constants.proto
+++ b/proto/src/metrics_constants.proto
@@ -4699,6 +4699,11 @@
     // OS: P
     AUTOFILL_SAVE_EXPLICITLY_TRIGGERED = 1229;
 
+    // OPEN: Settings > Network & Internet > Mobile network > Wi-Fi calling
+    // CATEGORY: SETTINGS
+    // OS: P
+    WIFI_CALLING_FOR_SUB = 1230;
+
     // Add new aosp constants above this line.
     // END OF AOSP CONSTANTS
   }