Remove useless use crate_name; imports.

A `crate_name::foo` path always works in 2018

components/profile/trace_dump.rs

@@ -5,7 +5,6 @@
 //! A module for writing time profiler traces out to a self contained HTML file.
 
 use profile_traits::time::{ProfilerCategory, TimerMetadata};
-use serde_json;
 use std::fs;
 use std::io::{self, Write};
 use std::path;