remove repetitive words

Signed-off-by: cui fliter <imcusg@gmail.com>

compiler/rustc_data_structures/src/sync/worker_local.rs

@@ -116,7 +116,7 @@ pub struct WorkerLocal<T> {
 
 // This is safe because the `deref` call will return a reference to a `T` unique to each thread
 // or it will panic for threads without an associated local. So there isn't a need for `T` to do
-// it's own synchronization. The `verify` method on `RegistryId` has an issue where the the id
+// it's own synchronization. The `verify` method on `RegistryId` has an issue where the id
 // can be reused, but `WorkerLocal` has a reference to `Registry` which will prevent any reuse.
 #[cfg(parallel_compiler)]
 unsafe impl<T: Send> Sync for WorkerLocal<T> {}