update `teal.slice` documentation on refactor branch

[chlebowa]

Several changes have been made during the refactor without amending documentation. This must be done before merging to main.

examples

FilteredData

#' - `logical`: variable of type `logical`, e.g. `ADSL$TRT_FLAG`
#'      exactly one option must be selected, `TRUE` or `FALSE`

👆 logical need not select one

teal_slice

@param multiple (`logical(1)`)\cr

👆 inconsistent format; see also

#' Special consideration is given to two fields: `fixed` and `locked`.

👆 rewrite after multiple

examples

• example apps in FilterState* and FilterStatesDF to define states with teal_slice

...

[gogonzo]

Hi @chlebowa I'm closing this up as duplicate of #314
Let's use primary issue