fix(docs): delete unnecessary title, fix invalid links

[steadily-worked]

hi,

1. when i enter to Columns Guide, i found that links of header groups, headers, footers returns 404. so i fixed it.

2. remove unnecessary title inside Headers Guide.

[KevinVandy]

There were a bunch of bad links as we transitioned from rewriting the docs in remix to TanStack Start, but these new links won't work. Closing in favor of other fixes.