Cleanup: Don't use string literals when character literals are needed

src/commands/CmdAliases.cpp

@@ -53,7 +53,7 @@ int CmdCompletionAliases::execute (std::string& output)
 {
   for (auto& alias : context.config)
     if (alias.first.substr (0, 6) == "alias.")
-      output += alias.first.substr (6) + "\n";
+      output += alias.first.substr (6) + '\n';
 
   return 0;
 }