Replace apt-get with apt (#7583)

README.md

@@ -125,7 +125,7 @@ Compiling

For Debian/Ubuntu:

    sudo apt-get install build-essential libirrlicht-dev cmake libbz2-dev libpng-dev libjpeg-dev libxxf86vm-dev libgl1-mesa-dev libsqlite3-dev libogg-dev libvorbis-dev libopenal-dev libcurl4-gnutls-dev libfreetype6-dev zlib1g-dev libgmp-dev libjsoncpp-dev
    sudo apt install build-essential libirrlicht-dev cmake libbz2-dev libpng-dev libjpeg-dev libxxf86vm-dev libgl1-mesa-dev libsqlite3-dev libogg-dev libvorbis-dev libopenal-dev libcurl4-gnutls-dev libfreetype6-dev zlib1g-dev libgmp-dev libjsoncpp-dev

For Fedora users:

@@ -137,7 +137,7 @@ You can install git for easily keeping your copy up to date.
If you don’t want git, read below on how to get the source without git.  
This is an example for installing git on Debian/Ubuntu:

    sudo apt-get install git
    sudo apt install git

For Fedora users: