Remove incorrect comment.

addon/content/sendMessage.js

@@ -99,7 +99,6 @@ function makeSender(compFields) {
     console.info(`makeSender: No identity found for sender ${compFields.from}, sending to ${compFields.to}`);
     return { send() {} };
   }
-  // Workaround for https://pep.foundation/jira/browse/ENGINE-776.
   if (!Services.prefs.getBoolPref(`mail.identity.${identity.key}.enableSync`, true)) {
     console.error(`makeSender: Sync message via disabled identity ${identity.email}`);
     return { send() {} };