Remove Extra Rectangle from ShinyDashboardPlus Carousel

[ixodid198]

I am using Rmarkdown and ShinyDashboardPlus to create a carousel of images. How do I remove the light gray rectangle around the slide in this carousel?

Rmarkdown

---
title: Carousel test
---

Here is a carousel

```{r, label='HIS-table', echo=FALSE, message=FALSE, warning=FALSE, results="asis"}
library("shiny")
library("shinydashboard")
library("shinydashboardPlus")

num_slides <- 1

chart_names <- "http://placehold.it/600x300/565656/ffffff&text=Slide+1"

items = Map(function(i) {carouselItem(
  tags$img(src = chart_names[i])
)}, 1:num_slides)


ui <- dashboardPagePlus(
  
  header = dashboardHeaderPlus(disable = TRUE ),
  sidebar = dashboardSidebar(width = 0 ),
  
  body = dashboardBody(
    carousel(indicators = TRUE,
             id = "mycarousel",
             .list = items
    )
  )
)

server <- function(input, output, session) {}

shinyApp(ui, server)

Here is the end of the carousel