fix(docs): use relearn notice shortcode instead of unsupported alert (#10364)

The Hugo relearn theme does not provide an "alert" shortcode, so the
docs deploy failed at the Build site step:

  failed to extract shortcode: template for shortcode "alert" not found
  docs/content/features/image-generation.md:106

Convert the vae_decode_only note to the theme-supported notice shortcode
used everywhere else in the docs.

Signed-off-by: Ettore Di Giacinto <mudler@localai.io>
Co-authored-by: Ettore Di Giacinto <mudler@localai.io>

Author: localai-bot

docs/content/features/image-generation.md

@@ -103,9 +103,9 @@ options:
 - "keep_clip_on_cpu:true"
 ```
 
-{{% alert note %}}
+{{% notice note %}}
 `vae_decode_only` is still accepted for backwards compatibility but is now a no-op: upstream removed the flag and the model decides automatically.
-{{% /alert %}}
+{{% /notice %}}
 
 #### Distributed inference (RPC workers)