[ImgBot] Optimize images

*Total -- 88.50kb -> 50.50kb (42.94%)

/content/assets/img/ELIXIR_logo_white_background.png -- 71.07kb -> 33.79kb (52.46%)
/content/assets/img/ELIXIR_logo_white_background.svg -- 9.89kb -> 9.22kb (6.72%)
/content/assets/img/noun_ecosystem_cycle_3389565.svg -- 2.53kb -> 2.51kb (0.81%)
/content/assets/img/EOSC.png -- 5.01kb -> 4.98kb (0.76%)

Signed-off-by: ImgBotApp <ImgBotHelp@gmail.com>

Author: ImgBotApp