git subrepo pull (merge) circuits/cpp/barretenberg (#1380)

Fix the barretenberg mirror action. Looks like commits went in too close
together, see #1382

` ./scripts/git_subrepo.sh pull circuits/cpp/barretenberg`
`git checkout origin/master -- .gitmodules`
`git commit`
This should always work if anyone needs to do this again. In more
complicated cases you may be instructed to do a merge. In this case the
commit just became overwritten.

```
subrepo:
  subdir:   "circuits/cpp/barretenberg"
  merged:   "96fb60558"
upstream:
  origin:   "https://github.com/AztecProtocol/barretenberg"
  branch:   "master"
  commit:   "d4ade2a5f"
git-subrepo:
  version:  "0.4.6"
  origin:   "???"
  commit:   "???"
```

circuits/cpp/barretenberg/.gitrepo

@@ -6,7 +6,7 @@
 [subrepo]
 	remote = https://github.com/AztecProtocol/barretenberg
 	branch = master
-	commit = 037dda3d254d56a20292d2bed5a9582d36c08427
+	commit = d4ade2a5f06a3abf3c9c2635946d7121cc2f64b4
 	parent = 5cf9c203e126b7613bf80960063d86cb9ee97954
 	method = merge
 	cmdver = 0.4.6