docs: update the image url

Author: lmxyy

docs/source/usage/ip_adapter.rst

@@ -1,7 +1,7 @@
 IP Adapter
 ==========
 
-.. image:: https://huggingface.co/datasets/nunchaku-tech/cdn/resolve/main/ComfyUI-nunchaku/workflows/nunchaku-flux.1-IP-adapter.png
+.. image:: https://huggingface.co/datasets/nunchaku-tech/cdn/resolve/main/ComfyUI-nunchaku/workflows/nunchaku-flux.1-ip-adapter.png
 
 Nunchaku supports `IP Adapter <hf_ip-adapterv2_>`_, an adapter achieving image prompt capability for the FLUX.1-dev