Remove kconfig-frontends installation from setup.sh

Tools/setup/ubuntu.sh

@@ -136,7 +136,6 @@ if [[ $INSTALL_NUTTX == "true" ]]; then
 		genromfs \
 		gettext \
 		gperf \
-		kconfig-frontends \
 		libelf-dev \
 		libexpat-dev \
 		libgmp-dev \
@@ -154,6 +153,12 @@ if [[ $INSTALL_NUTTX == "true" ]]; then
 		util-linux \
 		vim-common \
 		;
+	if [[ "${UBUNTU_RELEASE}" == "20.04" ]]; then
+		sudo DEBIAN_FRONTEND=noninteractive apt-get -y --quiet --no-install-recommends install \
+		kconfig-frontends \
+		;
+	fi
+
 
 	if [ -n "$USER" ]; then
 		# add user to dialout group (serial port access)