Use write_into_file for heap_profile helper.

Driveby fix write_to_file -> write_into_file in a DFATAL.

Change-Id: I1c487531aa00420e23ba0482789f7c6344c5ad75
diff --git a/tools/heap_profile b/tools/heap_profile
index e5b1f97..af59c67 100755
--- a/tools/heap_profile
+++ b/tools/heap_profile
@@ -96,6 +96,7 @@
 }}
 
 duration_ms: {duration}
+write_into_file: true
 flush_timeout_ms: 30000
 '''