Strip Closure Library licence from compressed file

[cpcallen]

Have we (or can we get) permission to strip the "Copyright The Closure Library Authors" copyright notice from the compiled output should closure/goog/base.js (or, after #5721 lands, closure/goog/base_minimal.js) be included in the compiler input?

(See issue #2412 which dealt with this same question in respect to the Google LLC and MIT notices.)

[cpcallen]

(This is mainly for consistency rather than filesize, since the notice only appears once in blockly_compressed.js—but it's a bit funny—and possibly confusing—for that to be the only copyright notice in the entire file.)

[NeilFraser]

If the roadmap involves the eventual removal of closure/goog/base.js in the future, then I'd advise accepting the temporary inclusion of this notice.

I have no special knowledge here; just an aversion to poking things which have the potential to backfire and cause major regressions for legal reasons.

[gonfunko]

Closing since closure/* is no more.