remove unused branding images

247e9efe · Benjamin Neff · Jonne Haß · bd888829 · bd888829 · bd888829
--- a/app/assets/images/branding/asterisk_white.png
+++ b/app/assets/images/branding/asterisk_white.png
--- a/app/assets/images/branding/ball_small.png
+++ b/app/assets/images/branding/ball_small.png
--- a/app/assets/images/branding/logo_white.png
+++ b/app/assets/images/branding/logo_white.png
--- a/app/assets/images/branding/logo_white2x.png
+++ b/app/assets/images/branding/logo_white2x.png
--- a/app/assets/images/branding/logo_white4x.png
+++ b/app/assets/images/branding/logo_white4x.png
--- a/app/assets/images/branding/white_on_grey.png
+++ b/app/assets/images/branding/white_on_grey.png