[draft][Ray clusters][docs] Fix TOCs/index pages/other small bugs

[cadedaniel]

Why are these changes needed?

Fixing small things that fell through the cracks

Related issue number

[cadedaniel]

Btw, are we going with "Ray cluster" instead of "Ray Cluster"?

I've been going with Ray cluster, wouldn't be surprised if missed something though.

[stephanie-wang]

Btw, are we going with "Ray cluster" instead of "Ray Cluster"?

I've been going with Ray cluster, wouldn't be surprised if missed something though.

Ah okay, sounds good! I've been using Ray Cluster, heh. But we can just do a find and replace at the end.

[cadedaniel]

@stephanie-wang I think I lost your changes when I force pushed after rebase. I'll add them again.

[cadedaniel]

@ericl this should be ready for merge! leaving to you per requested feature freeze