Set min_sdk_version to 29 in SampleRollbackApp.

Bug: 220204580
Test: manual
Change-Id: Ic9cb14662896d0aef47419419475cb1a36164bb0
diff --git a/tests/RollbackTest/SampleRollbackApp/Android.bp b/tests/RollbackTest/SampleRollbackApp/Android.bp
index a18488d..074c7bc 100644
--- a/tests/RollbackTest/SampleRollbackApp/Android.bp
+++ b/tests/RollbackTest/SampleRollbackApp/Android.bp
@@ -29,4 +29,5 @@
     resource_dirs: ["res"],
     certificate: "platform",
     sdk_version: "system_current",
+    min_sdk_version: "29",
 }