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}
diff --git a/docs/testing/layout_tests_with_manual_fallback.md b/docs/testing/layout_tests_with_manual_fallback.md
index 0d8e3a6..74aa2f9 100644
--- a/docs/testing/layout_tests_with_manual_fallback.md
+++ b/docs/testing/layout_tests_with_manual_fallback.md
@@ -11,7 +11,7 @@
 A popular pattern used in these tests is to rely on the user to perform some
 manual steps in order to run the test case in a normal browser session. These
 tests are effectively
-[manual tests](http://web-platform-tests.org/writing-tests/manual.html), with
+[manual tests](https://web-platform-tests.org/writing-tests/manual.html), with
 additional JavaScript code that automatically performs the desired manual steps,
 when loaded in an environment that exposes the needed testing APIs.