Express cache cleanup (#1142)

## Description of change

Remove unneeded todo

Relevant issues:
#1141 (comment)

## Does this change impact existing behavior?

No

## Does this change need a changelog entry in any of the crates?

No

---

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(DCO)](https://developercertificate.org/).

Signed-off-by: Simon Beal <[email protected]>

mountpoint-s3/src/data_cache/express_data_cache.rs

@@ -62,8 +62,6 @@ where
     Client: ObjectClient + Send + Sync + 'static,
 {
     /// Create a new instance.
-    ///
-    /// TODO: consider adding some validation of the bucket.
     pub fn new(client: Client, config: ExpressDataCacheConfig, source_bucket_name: &str, bucket_name: &str) -> Self {
         Self {
             client,