Adding Supplement:Apache-2.0 to chromium license allowlist.

The 'Supplement:Apache-2.0' contains the full license text and is the preferred version over just 'Apache-2.0'.

Change-Id: Ie4566ffdcd20771a0170190270d8d45e1b77980d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/6040532
Reviewed-by: Jordan Brown <rop@google.com>
Reviewed-by: Rachael Newitt <renewitt@google.com>
Commit-Queue: Rachael Newitt <renewitt@google.com>
Auto-Submit: Jordan Brown <rop@google.com>

metadata/fields/custom/license_allowlist.py

@@ -10,6 +10,7 @@
 ALLOWED_SPDX_LICENSES = frozenset([
     "APSL-2.0",
     "Apache-2.0",
+    "Supplement:Apache-2.0",
     "BSD-2-Clause",
     "BSD-2-Clause-FreeBSD",
     "BSD-3-Clause",