"Links to the multipage version of the specification are unfortunately
likely to break over time."
-- https://html.spec.whatwg.org/multipage/asefij.html
This commit removes all references to the specific pages when viewing
WHATWG using multipage mode. I went through all these links and they
redirect fine.
Regex used to generate this commit:
`s_whatwg.org/multipage/.*#_whatwg.org/multipage/#_g`
Extracted this out of #5649
This commit was created with the following commands:
```
find . -iname "*.webidl" -type f -print0 | xargs -0 sed -i '' 's/http:\(.*\)whatwg.org/https:\1whatwg.org/g'
```
```
find . -iname "*.rs" -type f -print0 | xargs -0 sed -i '' 's/http:\(.*\)whatwg.org/https:\1whatwg.org/g'
```
