Remove license from within source file

The license was removed from `binary_heap.rs` in rust-lang/rust#57108
after it was determined that the per-file license headers were not
necessary.  See also discussion in rust-lang/rust PRs #53654, #53617,
and #43498.

src/binary_heap.rs

@@ -1,13 +1,3 @@
-// Copyright 2013-2014 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
 //! A priority queue implemented with a binary heap.
 //!
 //! Note: This version is folked from Rust standartd library, which only supports