Change "Content Warning" to "Write your warning here" (#4313)

Change the placeholder used in the content warning field from "Content Warning" to "Write your warning here". This change should made it easier to understand what the field is about.

Change le message de substitution utilisé dans le champ d’avertissement de « Avertissement » à « Écrivez ici votre avertissement ». Ce changement devrait rendre plus évidente la fonction du champ.

app/javascript/mastodon/locales/en.json

@@ -45,7 +45,7 @@
   "compose_form.publish_loud": "{publish}!",
   "compose_form.sensitive": "Mark media as sensitive",
   "compose_form.spoiler": "Hide text behind warning",
-  "compose_form.spoiler_placeholder": "Content warning",
+  "compose_form.spoiler_placeholder": "Write your warning here",
   "confirmation_modal.cancel": "Cancel",
   "confirmations.block.confirm": "Block",
   "confirmations.block.message": "Are you sure you want to block {name}?",

app/javascript/mastodon/locales/fr.json

@@ -45,7 +45,7 @@
   "compose_form.publish_loud": "{publish}!",
   "compose_form.sensitive": "Marquer le média comme délicat",
   "compose_form.spoiler": "Masquer le texte derrière un avertissement",
-  "compose_form.spoiler_placeholder": "Avertissement",
+  "compose_form.spoiler_placeholder": "Écrivez ici votre avertissement",
   "confirmation_modal.cancel": "Annuler",
   "confirmations.block.confirm": "Bloquer",
   "confirmations.block.message": "Confirmez vous le blocage de {name} ?",