Fix RadioGroup example code

see https://twitter.com/adamwathan/status/1382433596615577600

Author: philippbosch

src/pages/headless-ui-v1/index.mdx

@@ -106,17 +106,17 @@ function MyRadioGroup() {
       <RadioGroup.Label>Plan</RadioGroup.Label>
       <RadioGroup.Option value="startup">
         {({ checked }) => (
-          <span className={`${checked} ? 'bg-blue-200' : ''`}>Startup</span>
+          <span className={checked ? 'bg-blue-200' : ''}>Startup</span>
         )}
       </RadioGroup.Option>
       <RadioGroup.Option value="business">
         {({ checked }) => (
-          <span className={`${checked} ? 'bg-blue-200' : ''`}>Business</span>
+          <span className={checked ? 'bg-blue-200' : ''}>Business</span>
         )}
       </RadioGroup.Option>
       <RadioGroup.Option value="enterprise">
         {({ checked }) => (
-          <span className={`${checked} ? 'bg-blue-200' : ''`}>Enterprise</span>
+          <span className={checked ? 'bg-blue-200' : ''}>Enterprise</span>
         )}
       </RadioGroup.Option>
     </RadioGroup>