Update draft-irtf-cfrg-vdaf.md

Co-authored-by: Christopher Patton <[email protected]>

draft-irtf-cfrg-vdaf.md

@@ -2404,7 +2404,7 @@ def shard_with_joint_rand(Prio3, meas, nonce, seeds):
 {: #prio3-shard-with-joint-rand title="Sharding an encoded measurement with joint randomness."}
 
 The difference between this procedure and previous one is that here we compute
-joint randomnesses `joint_rands`, split into multiple `joint_rand`
+joint randomnesses `joint_rands`, split it into multiple `joint_rand`,
 and pass each `joint_rand` to the proof generationg algorithm.
 (In {{prio3-shard-without-joint-rand}} the joint randomness is the empty
 vector, `[]`.) This requires generating an additional value, called the