increase plugin version to 0.4.0-alpha.4

Author: duffney

.github/workflows/test-azure-kv.yml

@@ -17,7 +17,7 @@ jobs:
           key_name: 'example'
           certificate_key_id: 'https://example-kv.vault.azure.net/keys/exampleCert/516954296d4d72db64644b2ab35721c2'
           plugin_name: 'notation-azure-kv'
-          plugin_version: '0.3.1-alpha.1'
+          plugin_version: '0.4.0-alpha.4'
       - name: check version
         run: notation --version
       - name: check plugins