[ImgBot] Optimize images

*Total -- 224.26kb -> 168.96kb (24.66%)

/mails/pre_release_week_1/app-dashboard.png -- 43.09kb -> 32.13kb (25.43%)
/mails/pre_release_week_1/app-explorer.png -- 181.17kb -> 136.83kb (24.47%)

Signed-off-by: ImgBotApp <[email protected]>

Author: ImgBotApp