fix: add missing kind field to metadata.yaml

The metadata.yaml file was missing the required 'kind: Metadata' field,
which caused clusterctl init --infrastructure azure to fail with:
'unexpected kind "" for provider infrastructure-azure (expected "Metadata")'

This fix adds the missing kind field to resolve the clusterctl initialization error.

Fixes: clusterctl init --infrastructure azure validation error

Author: zoroglucihat

metadata.yaml

@@ -4,6 +4,7 @@
 #
 # update this file only when a new major or minor version is released
 apiVersion: clusterctl.cluster.x-k8s.io/v1alpha3
+kind: Metadata
 releaseSeries:
   - major: 0
     minor: 3