Update toasts.md (#32782)
Update toasts.md (#32782)

* dropped mention of `backdrop-filter`
* changed mention of `.text-white` to `.btn-close-white` on close button
GerHobbelt/bootstrap,coliff/bootstrap,GerHobbelt/bootstrap,coliff/bootstrap,m5o/bootstrap,m5o/bootstrap,tjkohli/bootstrap,twbs/bootstrap,GerHobbelt/bootstrap,inway/bootstrap,inway/bootstrap,tjkohli/bootstrap,twbs/bootstrap,inway/bootstrap