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_tips.md b/docs/testing/layout_tests_tips.md
index fcda5dd8..69efd16 100644
--- a/docs/testing/layout_tests_tips.md
+++ b/docs/testing/layout_tests_tips.md
@@ -20,7 +20,7 @@
 ## General Principles
 
 This section contains guidelines adopted from
-[web-platform-tests documentation](http://web-platform-tests.org/writing-tests/general-guidelines.html)
+[web-platform-tests documentation](https://web-platform-tests.org/writing-tests/general-guidelines.html)
 and
 [WebKit's Wiki page on Writing good test cases](https://trac.webkit.org/wiki/Writing%20Layout%20Tests%20for%20DumpRenderTree),
 with Blink-specific flavoring.
@@ -93,7 +93,7 @@
 `testharness.js` makes a test self-describing when used correctly. Other types
 of tests, such as reference tests and
 [tests with manual fallback](./layout_tests_with_manual_fallback.md),
-[must be carefully designed](http://web-platform-tests.org/writing-tests/manual.html#requirements-for-a-manual-test)
+[must be carefully designed](https://web-platform-tests.org/writing-tests/manual.html#requirements-for-a-manual-test)
 to be self-describing.
 
 ### Minimal
@@ -107,7 +107,7 @@
 
 Tests should provide as much relevant information as possible when failing.
 `testharness.js` tests should prefer
-[rich assert_ functions](https://github.com/w3c/web-platform-tests/blob/master/docs/_writing-tests/testharness-api.md#list-of-assertions)
+[rich assert_ functions](https://web-platform-tests.org/writing-tests/testharness-api.html#list-of-assertions)
 to combining `assert_true()` with a boolean operator. Using appropriate
 `assert_` functions results in better diagnostic output when the assertion
 fails.