fix(tvix/store/blobsvc): drop stray println! debug statement

Change-Id: Ica073820ea8240d42ce8b979309f881af18a8cde
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8781
Reviewed-by: tazjin <tazjin@tvl.su>
Autosubmit: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI

tvix/store/src/blobservice/grpc.rs

@@ -423,7 +423,6 @@ mod tests {
         }
 
         let has = task::spawn_blocking(move || {
-            println!("client has?");
             client
                 .has(&fixtures::BLOB_A_DIGEST)
                 .expect("must not be err")