fix: certs namespace is not required

Author: laurci

docs/resources/certificates.mdx

@@ -13,7 +13,7 @@ If you want to know how to deploy a certificate you can check [Building & Deploy
 
 | Properties            | Type            | Required |
 | --------------------- | --------------- | :------: |
-| `namespace`           | `string`        |    ✓     |
+| `namespace`           | `string`        |          |
 | [`name`](#name)       | `string`        |    ✓     |
 | [`tags`](#tags)       | `array<string>` |          |
 | [`domains`](#domains) | `array<string>` |    ✓     |