onDownloadSubscription is not abstract anymore

Test: atest CtsSystemApiSignatureTestCases

Bug: 129975435
Change-Id: Ib32e990caacb8e9ae63b6906d9a7936d048bea36
(cherry picked from commit 6f65db794ce67b6e08c18887dd45d7288ad5c101)
diff --git a/29/system/api/android.txt b/29/system/api/android.txt
index 4d2cee2..e8c26fc 100644
--- a/29/system/api/android.txt
+++ b/29/system/api/android.txt
@@ -4471,7 +4471,7 @@
     ctor public EuiccService();
     method public android.os.IBinder onBind(android.content.Intent);
     method public abstract int onDeleteSubscription(int, java.lang.String);
-    method public abstract android.service.euicc.DownloadSubscriptionResult onDownloadSubscription(int, @NonNull android.telephony.euicc.DownloadableSubscription, boolean, boolean, @Nullable android.os.Bundle);
+    method public android.service.euicc.DownloadSubscriptionResult onDownloadSubscription(int, @NonNull android.telephony.euicc.DownloadableSubscription, boolean, boolean, @Nullable android.os.Bundle);
     method public abstract int onDownloadSubscription(int, android.telephony.euicc.DownloadableSubscription, boolean, boolean);
     method public abstract int onEraseSubscriptions(int);
     method public abstract android.service.euicc.GetDefaultDownloadableSubscriptionListResult onGetDefaultDownloadableSubscriptionList(int, boolean);