refactor(app, l10n): Remove unused strings

app/lib/l10n/app_en.arb

@@ -1,20 +1,8 @@
 {
-  "app_feature_coming_soon": "Have a little patience, this feature is coming soon!",
-
   "auth_choose_lab": "Please select your lab",
   "auth_sign_in": "Sign in",
   "auth_success": "Successfully imported data",
 
-  "err_could_not_launch": "Could not launch {url}",
-  "@err_could_not_launch": {
-    "description": "Error message when (auth-related) url cannot be launched.",
-    "placeholders": {
-      "url": {
-        "type": "String",
-        "example": "https://www.google.de"
-      }
-    }
-  },
   "err_could_not_retrieve_access_token": "An unexpected error occurred while retrieving the access token",
   "err_fetch_user_data_failed": "An unexpected error occurred while fetching your genomic data",
   "err_generic": "Error!",