fix: update oci-image to ghcr.io/canonical/identity-platform-login-ui:v0.21.3

Author: github-actions[bot]

charmcraft.yaml

@@ -20,7 +20,7 @@ resources:
   oci-image:
     type: oci-image
     description: OCI image for login-ui
-    upstream-source: ghcr.io/canonical/identity-platform-login-ui:v0.21.2
+    upstream-source: ghcr.io/canonical/identity-platform-login-ui:v0.21.3
 requires:
   ingress:
     interface: ingress