Update draft-irtf-cfrg-vdaf.md

Co-authored-by: David Cook <[email protected]>

draft-irtf-cfrg-vdaf.md

@@ -4359,7 +4359,7 @@ by at least `T` Clients for some threshold `T`. It invokes Poplar1 as follows:
    and sends them to the Aggregators.
 
 1. The Aggregators run VDAF preparation and aggregation on each of the reports
-   and sends their aggregate shares to the Collector.
+   and send their aggregate shares to the Collector.
 
 1. The Collector unshards the aggregate result, which consists of the hit count
    for each candidate prefix. For each prefix `p` with hit count at least `T`,