fix link in callout story

Author: ddecrulle

stories/CallOut.stories.tsx

@@ -9,7 +9,7 @@ const { meta, getStory } = getStoryFactory({
     "wrappedComponent": { CallOut },
     "description": `
 - [See DSFR documentation](https://www.systeme-de-design.gouv.fr/elements-d-interface/composants/mise-en-avant)
-- [See source code](//github.com/codegouvfr/react-dsfr/blob/main/src/CallOut.tsx)`,
+- [See source code](https://github.com/codegouvfr/react-dsfr/blob/main/src/CallOut.tsx)`,
     "disabledProps": ["lang"],
     "argTypes": {
         "title": {