Update web-platform-tests URLs after repo move

Part of https://bit.ly/wpt-transition.

Most of the changes were done as such:
```
git grep -l w3c/web-platform-tests | xargs sed -i 's#https://github.com/w3c/web-platform-tests#https://github.com/web-platform-tests/wpt#g'
git grep -lF 'web-platform-tests.org' | xargs sed -i 's#http://web-platform-tests.org#https://web-platform-tests.org#g'
```

The http => https changes included here because one such URL got
involved in the first after manual tweaks.

Change-Id: Ied8334b88e4a0936cd995a002bb2a502c04ecfc7
Reviewed-on: https://chromium-review.googlesource.com/1080510
Reviewed-by: Tim Volodine <[email protected]>
Reviewed-by: Robert Ma <[email protected]>
Reviewed-by: Rick Byers <[email protected]>
Commit-Queue: Philip Jägenstedt <[email protected]>
Cr-Commit-Position: refs/heads/master@{#563242}
29 files changed