Revert "restore support for ubuntu 20.04 in dependency installation scripts (cyberbotics#6736)" (cyberbotics#6739)

This reverts commit 8fd32fb.

Author: CoolSpy3

scripts/install/linux_compilation_dependencies.sh

@@ -15,9 +15,7 @@ apt update
 apt install --yes git lsb-release cmake swig libglu1-mesa-dev libglib2.0-dev libfreeimage3 libfreetype6-dev libxml2-dev libboost-dev libssh-gcrypt-dev libzip-dev libreadline-dev pbzip2 wget zip unzip python3 python3-pip libopenal-dev
 
 UBUNTU_VERSION=$(lsb_release -rs)
-if [[ $UBUNTU_VERSION == "20.04" ]]; then
-       apt install --yes libzip5 perl libtext-template-perl
-elif [[ $UBUNTU_VERSION == "22.04" || $UBUNTU_VERSION == "24.04" ]]; then
+if [[ $UBUNTU_VERSION == "22.04" || $UBUNTU_VERSION == "24.04" ]]; then
        apt install --yes libzip4 openssl
 else
        echo "Unsupported Linux version: dependencies may not be completely installed. Only the two latest Ubuntu LTS are supported."

scripts/install/linux_runtime_dependencies.sh

@@ -18,7 +18,7 @@ if [[ -z "$DISPLAY" ]]; then
 fi
 
 UBUNTU_VERSION=$(lsb_release -rs)
-if [[ $UBUNTU_VERSION == "20.04" || $UBUNTU_VERSION == "22.04" || $UBUNTU_VERSION == "24.04" ]]; then
+if [[ $UBUNTU_VERSION == "22.04" || $UBUNTU_VERSION == "24.04" ]]; then
        apt install --yes ffmpeg
 else
        echo "Unsupported Linux version: dependencies may not be completely installed. Only the two latest Ubuntu LTS are supported."