CODEOWNERS: Assign new pkg/l2announcer package to @cilium/sig-agent

This package needs a codeowner, assinging to @cilium/sig-agent since we
have no specific team for this feature and its a agent component.

Signed-off-by: Dylan Reimerink <dylan.reimerink@isovalent.com>

CODEOWNERS

@@ -438,6 +438,7 @@ jenkinsfiles @cilium/ci-structure
 /pkg/k8s/apis/cilium.io/v2/ @cilium/api @cilium/sig-k8s
 /pkg/kafka/ @cilium/proxy
 /pkg/kvstore/ @cilium/kvstore
+/pkg/l2announcer/ @cilium/sig-agent
 /pkg/labels @cilium/sig-policy @cilium/api
 /pkg/labelsfilter @cilium/sig-policy
 /pkg/launcher @cilium/sig-agent