message: Add consistent prefix in Compile Instructions
diff: @@ -56,7 +56,7 @@ git clone https://gitlab.redox-os.org/redox-os/ion/
  cd ion
  make
  sudo make install prefix=/usr
  -sudo make update-shells
  +sudo make update-shells prefix=/usr
  ```
  > To compile in DEBUG mode, pass `DEBUG=1` as an argument to `make`
  