tombstoned: clean up TODO on anr writes

audit logs indicate that "append" is still used, but not write.

From ToT master:
avc: granted { append } for comm="tombstoned" scontext=u:r:tombstoned:s0
tcontext=u:object_r:anr_data_file:s0 tclass=file

Bug: 32064548
Test: build
Change-Id: Id05853a8ae38b84deed4d8bcca5a72c64ce7fd7e

public/tombstoned.te

@@ -11,12 +11,7 @@ allow tombstoned domain:file r_file_perms;
 allow tombstoned tombstone_data_file:dir rw_dir_perms;
 allow tombstoned tombstone_data_file:file { create_file_perms link };
 
-# TODO: Remove append / write permissions. They were temporarily
-# granted due to a bug which appears to have been fixed.
-allow tombstoned anr_data_file:file { append write };
-auditallow tombstoned anr_data_file:file { append write };
-
 # Changes for the new stack dumping mechanism. Each trace goes into a
 # separate file, and these files are managed by tombstoned.
 allow tombstoned anr_data_file:dir rw_dir_perms;
-allow tombstoned anr_data_file:file { create getattr open link unlink };
+allow tombstoned anr_data_file:file { append create getattr open link unlink };