wg-notebooks: Rename group to wg-notebooks-leads (#420)
wg-notebooks: Rename group to wg-notebooks-leads (#420)

The GitHub group for team leads of wg-notebooks was mistakenly named
`wg-notebook-leads`. Rename to `wg-notebooks-leads`, same as other wgs.

Signed-off-by: Yannis Zarkadas <4575790e8e8b84da294884a87fd791e10dfc7d9d@arrikto.com>
kubeflow/internal-acls,kubeflow/internal-acls,kubeflow/internal-acls