chore: fix CODEOWNER group name (#22)

Invalid group name used for CODEOWNERS.

Closes

## By Submitting this PR I confirm:
- I am familiar with the [Contributing Guidelines](https://github.com/NVIDIA/NeMo-Agent-Toolkit/blob/develop/docs/source/resources/contributing/index.md).
- We require that all contributors "sign-off" on their commits. This certifies that the contribution is your original work, or you have rights to submit it under the same license, or a compatible license.
  - Any contribution which contains commits that are not Signed-Off will not be accepted.
- When the PR is ready for review, new or existing tests cover these changes.
- When the PR is ready for review, the documentation is up to date with these changes.

Authors:
  - Will Killian (https://github.com/willkill07)

Approvers:
  - David Gardner (https://github.com/dagardner-nv)

URL: #22

Author: willkill07

.github/CODEOWNERS

@@ -1,2 +1,2 @@
 # Default Approval rule
-* @nvidia/aiqtoolkit-developers
+* @nvidia/nat-developers