dot-dsl: Replace filter(p).next() with find(p) (#1024)
dot-dsl: Replace filter(p).next() with find(p) (#1024)

clippy::filter_next
https://rust-lang.github.io/rust-clippy/master/index.html#filter_next

Helps address https://github.com/exercism/rust/pull/1012
petertseng/exercism-rust,petertseng/exercism-rust,petertseng/exercism-rust,exercism/xrust,exercism/xrust