Update CODEOWNERS
Update CODEOWNERS

Remove non existing folders and align owners with the DEE observability group.
Keep Daniel Sanche as code owner for .github and cloud-shell folders until refactoring to the project is applied.
GoogleCloudPlatform/cloud-ops-sandbox,GoogleCloudPlatform/cloud-ops-sandbox,GoogleCloudPlatform/cloud-ops-sandbox,GoogleCloudPlatform/cloud-ops-sandbox,GoogleCloudPlatform/cloud-ops-sandbox,GoogleCloudPlatform/cloud-ops-sandbox,GoogleCloudPlatform/cloud-ops-sandbox