[src/doc/book] Drop unused images
[src/doc/book] Drop unused images

tsurai/cargo,vojtechkral/cargo,tshepang/cargo,tsurai/cargo,tshepang/cargo,tshepang/cargo,rustyhorde/cargo,eminence/cargo,rust-lang/cargo,achanda/cargo,rust-lang/cargo,nipunn1313/cargo,tsurai/cargo,rustyhorde/cargo,vojtechkral/cargo,vojtechkral/cargo,nipunn1313/cargo,achanda/cargo,achanda/cargo,eminence/cargo,rust-lang/cargo,tshepang/cargo,nipunn1313/cargo,nipunn1313/cargo,eminence/cargo,rust-lang/cargo,achanda/cargo,tsurai/cargo,rustyhorde/cargo,rustyhorde/cargo,tsurai/cargo,eminence/cargo,vojtechkral/cargo