Bug 1689494 - Don't include gmp-clearkey in test archives. r=releng-reviewers,jmaher

It's already part of Firefox, and makes the gtest initialization print
an error message because the one already in Firefox can't be
overwritten.

Differential Revision: https://phabricator.services.mozilla.com/D103475

python/mozbuild/mozbuild/action/test_archive.py

@@ -54,7 +54,6 @@ TEST_HARNESS_BINS = [
 TEST_HARNESS_DLLS = ["crashinjectdll", "mozglue"]
 
 GMP_TEST_PLUGIN_DIRS = [
-    "gmp-clearkey/**",
     "gmp-fake/**",
     "gmp-fakeopenh264/**",
 ]