Partial revert of "Update translations"

Put link params back as they should be.

// FREEBIE

_locales/fr/messages.json

@@ -277,11 +277,7 @@
         "message": "Commencez par installer <a $a_params$>Signal</a> sur votre téléphone Android. Nous lierons et synchroniserons vos appareils ensuite.",
         "description": "Prompt the user to install Signal on Android before linking",
         "placeholders": {
-            "play_store": {
-                "content": "$1",
-                "example": "href='http://example.com'"
-            },
-            "app_store": {
+            "a_params": {
                 "content": "$1",
                 "example": "href='http://example.com'"
             }