fix: Correct license headers in compiled output

It seems that the `!` in the header forces the compiler to keep it in
the output.  I believe older compiler releases did this purely based
on `@license`.

Issue #2638

This is a minimal backport to v2.5.x which only touches the compiled
wrapper.

Change-Id: I7f0e918caad10c9af689c9d07672b7fe9be7b2f3

build/wrapper.template.js

@@ -1,3 +1,9 @@
+/*! @license
+ * Shaka Player
+ * Copyright 2016 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
 (function() {
   // This is "window" in browsers and "global" in nodejs.
   // See https://github.com/google/shaka-player/issues/1445