Remove dead minijail_disable_ptrace() declaration.

Change-Id: Iee493a21252ef952c6d34ded1443ad9bbeb960d7
diff --git a/libminijail.h b/libminijail.h
index 49f7786..6eccb02 100644
--- a/libminijail.h
+++ b/libminijail.h
@@ -78,7 +78,6 @@
 void minijail_run_as_init(struct minijail *j);
 int minijail_write_pid_file(struct minijail *j, const char *path);
 void minijail_inherit_usergroups(struct minijail *j);
-void minijail_disable_ptrace(struct minijail *j);
 /*
  * Changes the jailed process's syscall table to the alt_syscall table
  * named |table|.