Remove some outdated comments about dependency tracking from cstore_impl.
Remove some outdated comments about dependency tracking from cstore_impl.

graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust