Sync web-platform-tests PR 21677 into mozilla-central (this bug is closed when the sync is complete).

PR: https://github.com/web-platform-tests/wpt/pull/21677
Details from upstream follow.

Joshua Bell <jsbell@chromium.org> wrote:

Encoding: Deflake some web platform tests via sharding

encoding/api-invalid-label.any.js had 3287 subtests
encoding/textdecoder-fatal-single-byte.any.js had 7169 subtests

Pragmatically, the encoding tests need to sharded down to 1000
or they flakily timeout (e.g. on win debug and MSAN bots). Apply
that here, and update expectations.

Bug: 862938, 517704
Change-Id: I1b1bd13dd997700791ec25de9d0c75c1e5f72960

Reviewed-on: https://chromium-review.googlesource.com/2045144
WPT-Export-Revision: 7d9247606dbb110d5b6795842457683b1053fa4e

CI Results

Ran 0 Firefox configurations based on mozilla-central, and Firefox, Chrome, and Safari on GitHub CI

Total 24 tests and 1000 subtests

Status Summary

Firefox

OK : 24
PASS: 20908

Chrome

OK : 24
PASS: 20908

Safari

OK : 24
PASS: 20608
FAIL: 300

Links

GitHub PR Head
GitHub PR Base

https://hg.mozilla.org/mozilla-central/rev/780d607e3b25