Fixing broken HTML documentation links

[egthomas]

This pull request fixes the few remaining broken links in the HTML documentation - no code functionality is modified.

[ksterne]

While testing this, I'm reminded of what we brought up in #532. In theory we probably shouldn't making updates to something we're deprecating, but the complete removal can happen in another PR. It's good to correct the issue so that it's right somewhere in the git history.

Agreed that this doesn't break compilation. I didn't initially look at the changes close enough to realize the fix to the broken link was to just remove any of the links. Does the rplot documentation not exist anymore? I'm sorry if I'm forgetting something, but I also didn't find any discussion or PR on it when searching this repo. It's OK if the documentation doesn't exist, just was surprised that they didn't exist at all.

[egthomas]

Does the rplot documentation not exist anymore?

No, rplot was from the pre-3.x era of RST and from what I can tell it evolved into other libraries such as grplot, which has no documentation (and probably never will).