chore: Add bbup version mapping for Noir v1.0.0-beta.21

Author: Savio-Sou

barretenberg/bbup/bb-versions.json

@@ -1,4 +1,5 @@
 {
+  "1.0.0-beta.21": "5.0.0-nightly.20260324",
   "1.0.0-beta.20": "5.0.0-nightly.20260324",
   "1.0.0-beta.19": "4.0.0-nightly.20260120",
   "1.0.0-beta.18": "3.0.0-nightly.20260102",