chore(bb): skip Chonk VK consistency check on aztec-packages-private (#22910)

The `test_chonk_standalone_vks_havent_changed.sh` test compares
freshly-generated Chonk VKs against a set of inputs pinned in S3 by the
public repo's release flow. The private fork
(`AztecProtocol/aztec-packages-private`) carries divergent circuits, so
the check reliably fails there with `VK change detected` even though
nothing is actually wrong.

Skip emitting the test command from `test_cmds_native` when
`GITHUB_REPOSITORY` is the private fork. The script itself is untouched,
so a developer can still run it by hand if they want.

`GITHUB_REPOSITORY` is already the canonical "which repo are we in"
signal across `ci3/` and the `.github/workflows/*-private.yml`
workflows, so this matches existing patterns. The lowercase comparison
guards against any case variance (GitHub preserves casing but other
paths in `ci3/bootstrap_ec2` use lowercase fallbacks).

Details / reasoning:
https://gist.github.com/AztecBot/5ff607e2afff36a41a9f4d0c43e508cb

ClaudeBox log: https://claudebox.work/s/7dc66040213e399f?run=1

Author: ludamad

barretenberg/cpp/bootstrap.sh

@@ -265,7 +265,11 @@ function test_cmds_native {
       done || (echo "Failed to list tests in $bin" && exit 1)
   done
 
-  echo "$hash barretenberg/cpp/scripts/test_chonk_standalone_vks_havent_changed.sh"
+  # The pinned IVC inputs / VKs live in the public repo; the private fork
+  # carries divergent circuits so the check is expected to fail there.
+  if [[ "${GITHUB_REPOSITORY,,}" != "aztecprotocol/aztec-packages-private" ]]; then
+    echo "$hash barretenberg/cpp/scripts/test_chonk_standalone_vks_havent_changed.sh"
+  fi
 }
 
 function test_cmds_wasm_threads {