Merge pull request #483 from external-secrets/chore/promote-vault

Update README.md - promote vault

README.md

@@ -30,7 +30,7 @@ Multiple people and organizations are joining efforts to create a single Externa
 | ------------------------------------------------------------------------ | :-------: | ---------------------------------------------: |
 | [AWS SM](https://external-secrets.io/provider-aws-secrets-manager/)      |   alpha   | [ESO Org](https://github.com/external-secrets) |
 | [AWS PS](https://external-secrets.io/provider-aws-parameter-store/)      |   alpha   | [ESO Org](https://github.com/external-secrets) |
-| [Hashicorp Vault](https://external-secrets.io/provider-hashicorp-vault/) |   alpha   | [ESO Org](https://github.com/external-secrets) |
+| [Hashicorp Vault](https://external-secrets.io/provider-hashicorp-vault/) |   stable   | [ESO Org](https://github.com/external-secrets) |
 | [GCP SM](https://external-secrets.io/provider-google-secrets-manager/)   |   alpha   | [ESO Org](https://github.com/external-secrets) |
 
 ### Community maintained: