Remove old and unused vignettes

[IndrajeetPatil]

Closes #953

For future reference:

If you want to check these out, do-
git checkout v1.0.0

[IndrajeetPatil]

Okay, pkgdown build is succeeding now.

[lorenzwalthert]

Thanks. Also please add a NEWS.md entry next time 😊

[IndrajeetPatil]

Ah, sorry, didn't realize that these were user-facing; I thought you were already skipping them on CRAN.

I can update NEWS in the PR for #954.

[github-actions]

This is how benchmark results would change (along with a 95% confidence interval in relative change) if 3178326 is merged into main:

•   :ballot_box_with_check:cache_applying: 25ms -> 24.8ms [-3.24%, +1.46%]
•   :ballot_box_with_check:cache_recording: 1.06s -> 1.07s [-1.2%, +3.09%]
•   :ballot_box_with_check:without_cache: 2.94s -> 2.91s [-3.1%, +1.38%]

Further explanation regarding interpretation and methodology can be found in the documentation.