Delete only directories (not files) in a directory

gistfile1.sh

#!/bin/bash

# Make a directory with some test directories and files inside
mkdir test
cd test
mkdir test1
mkdir test2
mkdir test3
touch hello.txt
touch goodbye.txt
touch samurai.txt

ls
# goodbye.txt  hello.txt    samurai.txt  test1        test2        test3

# Delete the directories only
rm -r */

ls
# goodbye.txt  hello.txt    samurai.txt