fix: Don't add `bslib-gap-spacing` when card body is not fillable

[gadenbuie]

When card_body(fillable = FALSE, ...) we should not be adding the bslib-gap-spacing class to the card body container.

App Example

```r library(shiny) # library(bslib) pkgload::load_all() library(leaflet) ui <- page_fillable( card( class = "text-bg-light", # max_height = "400px", card_body( fillable = FALSE, h3("Lehigh University"), lorem::ipsum(3, 1:3 + 1), actionButton("visit", "Visit School") ), card_body( leafletOutput("map_lehigh"), ) ) ) server <- function(input, output, session) { output$map_lehigh <- renderLeaflet({ lat <- 40.60682 long <- -75.38024 name <- "Lehigh University" leaflet() |> addTiles() |> setView(lng = long, lat = lat, zoom = 13) |> addMarkers(lng = long, lat = lat, popup = name) }) } shinyApp(ui, server) ```

Before	After

[cpsievert]

Looks like there at least a couple other places we unconditionally add this class -- should we be doing the same there?

[gadenbuie]

Looks like there at least a couple other places we unconditionally add this class -- should we be doing the same there?

Yeah probably! If you have the time to add those to this PR, that'd be appreciated.