Remove docs for HTML support in frontend/custom panel (#14431)

source/_integrations/frontend.markdown

@@ -37,10 +37,6 @@ frontend:
             description: The CSS identifier.
             required: true
             type: [list, string]
-  extra_html_url:
-    description: "DEPRECATED List of additional [resources](/developers/frontend_creating_custom_ui/) to load in `latest` javascript mode."
-    required: false
-    type: list
   extra_module_url:
     description: "List of additional javascript modules to load in `latest` javascript mode."
     required: false
@@ -80,7 +76,7 @@ There are 2 themes-related services:
 
  - `frontend.reload_themes`: reloads theme configuration from your `configuration.yaml` file.
  - `frontend.set_theme`: sets backend-preferred theme name.
- 
+
  ### Service `set_theme`
 
 | Service data attribute | Description                                                                                         |

source/_integrations/panel_custom.markdown

@@ -77,8 +77,4 @@ trust_external_script:
   required: false
   default: false
   type: boolean
-webcomponent_path:
-  description: "*DEPRECATED* The HTML path to your component. If omitted will default to `<config dir>/panels/<component name>.html` This cannot be used in combination with either `js_url` and `module_url`."
-  required: false
-  type: string
 {% endconfiguration %}