Remove text-to-image tag

WebUIs build on top of diffusers start to rely on the HF Hub client library to filter for models. This one should not be displayed when listing "text-to-image" models:
```py
import huggingface_hub as hf
hf_api = hf.HfApi()
model_filter = hf.ModelFilter(
model_name="",
task='text-to-image',
tags='stable-diffusion',
library=['diffusers', 'stable-diffusion'],
)
res = hf_api.list_models(filter=model_filter, full=True, limit=200, sort="downloads", direction=-1)
```

README.md

@@ -2,7 +2,6 @@
 license: openrail++
 tags:
 - stable-diffusion
-- text-to-image
 inference: false
 ---